Calling exit() on a memory failure probably made sense for the
standalone preprocessor, but doesn't seem too appealing as part of
the GL library. Also, we don't use it in the main compiler.
We define the YY_NO_INPUT macro to avoid one needless function being
generated.
for the other needless functions, (yyunput and yy_top_state), we add a
new UNREACHABLE start condition and call these functions from an
action there. This doesn't change functionality at all, (since we
never enter the UNREACHABLE start condition), but makes the compiler
stop complaining about these two functions being defined but not used.
It's really a bug in flex that these functions are generated with neither
a declaration nor the 'static' keyword, but we can at least avoid the
warnings this way.
Previously, if the outer #ifdef/#ifndef evaluated to false, the inner
directive would not be parsed correctly, (the identifier as the subject
of the #ifdef/#ifndef would inadvertently be skipped along with the other
content correctly being skipped).
We fix this by setting the lexing_if state in each case here.
We also add a new test to the test suite to ensure that this case is tested.
