tests/make: clean up, explain and reorganize several tests

tests/make: test triple negation in '.ifndef'

tests/make: force line-based diagnostics to be listed in the tests

This way, contradictions between the intended output and the actual
output are closer together and have a better chance of being spotted.

make(1): indent directives like .info, .if, .for consistently

Done by "pkglint -F *.mk", no manual corrections.

make(1): revert previous commit

It had accidentally reverted all the work from the past few days.

make(1): fix double-free bug in -DCLEANUP mode (since 2020-10-02)

The bug had been introduced with dir.c 1.155 on 2020-10-02 22:20:25. In
that commit, openDirectories was replaced with a combination of a list
with a hash table, for more efficient lookup by name.

Upon cleanup, OpenDirs_Done is called, which in turn called
Dir_ClearPath. Dir_ClearPath takes full ownership of the given list and
empties it. This was no problem before since afterwards the list was
empty and calling Lst_Free just frees the remaining list pointer.

With OpenDirs, this list was combined with a hash table, and the hash
table contains the list nodes, assuming that the OpenDirs functions have
full ownership of both the list and the hash table. This assumption was
generally correct, except for the one moment during cleanup where full
ownership of the list was passed to Dir_ClearPath, while the hash table
still contained pointers to the (now freed) list nodes. This by itself
was not a problem since the hash table would be freed afterwards. But
as part of Dir_ClearPath, OpenDirs_Remove was called, which looked up
the freed directory by name and now found the freed list node, trying to
free it again. Boom.

Fixed by replacing the call to Dir_ClearPath with code that only frees
the directories, without giving up control over the list.

make(1): add tests for .ifndef and .ifnmake

make(1): describe the purpose of each newly added unit test dummy

make(1): add dummies for fine-grained tests, one per single feature

The test names have been derived from the current manual page.

All these tests are dummies right now, and the code from the existing
tests will be moved into the new tests step by step.

This is done to prevent modmisc, escape, varmod-edge and varmisc from
growing without any bounds, and to reduce the side-effects of one test
to the others.

tests/make: test triple negation in '.ifndef'

tests/make: force line-based diagnostics to be listed in the tests

This way, contradictions between the intended output and the actual
output are closer together and have a better chance of being spotted.

make(1): indent directives like .info, .if, .for consistently

Done by "pkglint -F *.mk", no manual corrections.

make(1): revert previous commit

It had accidentally reverted all the work from the past few days.

make(1): fix double-free bug in -DCLEANUP mode (since 2020-10-02)

The bug had been introduced with dir.c 1.155 on 2020-10-02 22:20:25. In
that commit, openDirectories was replaced with a combination of a list
with a hash table, for more efficient lookup by name.

Upon cleanup, OpenDirs_Done is called, which in turn called
Dir_ClearPath. Dir_ClearPath takes full ownership of the given list and
empties it. This was no problem before since afterwards the list was
empty and calling Lst_Free just frees the remaining list pointer.

With OpenDirs, this list was combined with a hash table, and the hash
table contains the list nodes, assuming that the OpenDirs functions have
full ownership of both the list and the hash table. This assumption was
generally correct, except for the one moment during cleanup where full
ownership of the list was passed to Dir_ClearPath, while the hash table
still contained pointers to the (now freed) list nodes. This by itself
was not a problem since the hash table would be freed afterwards. But
as part of Dir_ClearPath, OpenDirs_Remove was called, which looked up
the freed directory by name and now found the freed list node, trying to
free it again. Boom.

Fixed by replacing the call to Dir_ClearPath with code that only frees
the directories, without giving up control over the list.

make(1): add tests for .ifndef and .ifnmake

make(1): describe the purpose of each newly added unit test dummy

make(1): add dummies for fine-grained tests, one per single feature

The test names have been derived from the current manual page.

All these tests are dummies right now, and the code from the existing
tests will be moved into the new tests step by step.

This is done to prevent modmisc, escape, varmod-edge and varmisc from
growing without any bounds, and to reduce the side-effects of one test
to the others.

make(1): indent directives like .info, .if, .for consistently

Done by "pkglint -F *.mk", no manual corrections.

make(1): revert previous commit

It had accidentally reverted all the work from the past few days.

make(1): fix double-free bug in -DCLEANUP mode (since 2020-10-02)

The bug had been introduced with dir.c 1.155 on 2020-10-02 22:20:25. In
that commit, openDirectories was replaced with a combination of a list
with a hash table, for more efficient lookup by name.

Upon cleanup, OpenDirs_Done is called, which in turn called
Dir_ClearPath. Dir_ClearPath takes full ownership of the given list and
empties it. This was no problem before since afterwards the list was
empty and calling Lst_Free just frees the remaining list pointer.

With OpenDirs, this list was combined with a hash table, and the hash
table contains the list nodes, assuming that the OpenDirs functions have
full ownership of both the list and the hash table. This assumption was
generally correct, except for the one moment during cleanup where full
ownership of the list was passed to Dir_ClearPath, while the hash table
still contained pointers to the (now freed) list nodes. This by itself
was not a problem since the hash table would be freed afterwards. But
as part of Dir_ClearPath, OpenDirs_Remove was called, which looked up
the freed directory by name and now found the freed list node, trying to
free it again. Boom.

Fixed by replacing the call to Dir_ClearPath with code that only frees
the directories, without giving up control over the list.

make(1): add tests for .ifndef and .ifnmake

make(1): describe the purpose of each newly added unit test dummy

make(1): add dummies for fine-grained tests, one per single feature

The test names have been derived from the current manual page.

All these tests are dummies right now, and the code from the existing
tests will be moved into the new tests step by step.

This is done to prevent modmisc, escape, varmod-edge and varmisc from
growing without any bounds, and to reduce the side-effects of one test
to the others.

make(1): revert previous commit

It had accidentally reverted all the work from the past few days.

make(1): fix double-free bug in -DCLEANUP mode (since 2020-10-02)

The bug had been introduced with dir.c 1.155 on 2020-10-02 22:20:25. In
that commit, openDirectories was replaced with a combination of a list
with a hash table, for more efficient lookup by name.

Upon cleanup, OpenDirs_Done is called, which in turn called
Dir_ClearPath. Dir_ClearPath takes full ownership of the given list and
empties it. This was no problem before since afterwards the list was
empty and calling Lst_Free just frees the remaining list pointer.

With OpenDirs, this list was combined with a hash table, and the hash
table contains the list nodes, assuming that the OpenDirs functions have
full ownership of both the list and the hash table. This assumption was
generally correct, except for the one moment during cleanup where full
ownership of the list was passed to Dir_ClearPath, while the hash table
still contained pointers to the (now freed) list nodes. This by itself
was not a problem since the hash table would be freed afterwards. But
as part of Dir_ClearPath, OpenDirs_Remove was called, which looked up
the freed directory by name and now found the freed list node, trying to
free it again. Boom.

Fixed by replacing the call to Dir_ClearPath with code that only frees
the directories, without giving up control over the list.

make(1): add tests for .ifndef and .ifnmake

make(1): describe the purpose of each newly added unit test dummy

make(1): add dummies for fine-grained tests, one per single feature

The test names have been derived from the current manual page.

All these tests are dummies right now, and the code from the existing
tests will be moved into the new tests step by step.

This is done to prevent modmisc, escape, varmod-edge and varmisc from
growing without any bounds, and to reduce the side-effects of one test
to the others.

make(1): describe the purpose of each newly added unit test dummy

make(1): add dummies for fine-grained tests, one per single feature

The test names have been derived from the current manual page.

All these tests are dummies right now, and the code from the existing
tests will be moved into the new tests step by step.

This is done to prevent modmisc, escape, varmod-edge and varmisc from
growing without any bounds, and to reduce the side-effects of one test
to the others.