Copy head@r302406 to stable/11 as part of the 11.0-RELEASE cycle.
Prune svn:mergeinfo from the new branch, as nothing has been merged
here.

Additional commits post-branch will follow.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Integrate tools/regression/lib/libc/gen into the FreeBSD test suite
as lib/libc/tests/gen

The code in test-fnmatch that was used for generating:

- bin/sh/tests/builtins/case2.0
- bin/sh/tests/builtins/case3.0

has been left undisturbed. The target `make sh-tests` has been moved over
from tools/regression/lib/libc/gen/Makefile to
lib/libc/tests/gen/Makefile and made into a PHONY target

case2.0 and case3.0 test input generation isn't being done automatically.
This needs additional discussion.

MFC after: 1 week
Sponsored by: EMC / Isilon Storage Division

wordexp(): Improve some error codes.

Distinguish between WRDE_BADVAL and WRDE_SYNTAX based on when the error
occurred (parsing or execution), not based on whether WRDE_UNDEF was passed.

Also, return WRDE_NOSPACE for a few more unexpected results from sh.

wordexp(): Add testcase for non-default IFS in environment.

The non-default IFS is expected to be used.

MFC after: 1 week

wordexp(): Fix syntax validation for backslashes in single-quotes.

wordexp(): Remove wrong IFS usage.

Words in shell script are separated by spaces or tabs independent of the
value of IFS. The value of IFS is only relevant for the result of
substitutions. Therefore, there should be a space between 'wordexp' and the
words to be expanded, not an IFS character.

Paranoia might dictate that the shell ignore IFS from the environment (even
though our sh currently uses it), so do not depend on it in the new test
case.

wordexp(3): fix some bugs with signals and long outputs
* retry various system calls on EINTR
* retry the rest after a short read (common if there is more than about 1K
of output)
* block SIGCHLD like system(3) does (note that this does not and cannot
work fully in threaded programs, they will need to be careful with wait
functions)

PR: 90580
MFC after: 1 month

Fix an amusing typo that has prevented this from compiling since 2004.

Add a regression test for wordexp() and wordfree().