tests/make: replace 'variable expression' with 'expression'

Each expression is based on a variable, there's no need for the
verbosity. The wording in make's diagnostics will be changed in a
follow-up commit.

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.

tests/make: clean up comments, extend a few tests

make: do not evaluate misplaced expressions in malformed conditions

This change only affects the behavior for parse errors. Syntactically
well-formed conditions work exactly as before.

make(1): add test for variable expressions after a parse error

These variable expressions don't need to be expanded, and they aren't.

make(1): add test for parsing the end of a condition

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.

tests/make: clean up comments, extend a few tests

make: do not evaluate misplaced expressions in malformed conditions

This change only affects the behavior for parse errors. Syntactically
well-formed conditions work exactly as before.

make(1): add test for variable expressions after a parse error

These variable expressions don't need to be expanded, and they aren't.

make(1): add test for parsing the end of a condition

make: do not evaluate misplaced expressions in malformed conditions

This change only affects the behavior for parse errors. Syntactically
well-formed conditions work exactly as before.

make(1): add test for variable expressions after a parse error

These variable expressions don't need to be expanded, and they aren't.

make(1): add test for parsing the end of a condition