why no _GLIBCXX_USE_C99_STDLIB?

[Andriy Gapon]

cstdlib provides functions like std::strtoll only if _GLIBCXX_USE_C99 is defined.
Judging from acinclude.m4  _GLIBCXX_USE_C99 gets defined only if all the following
are set to yes: glibcxx_cv_c99_math,
glibcxx_cv_c99_complex, glibcxx_cv_c99_stdio, glibcxx_cv_c99_stdlib and
glibcxx_cv_c99_wchar.

So if a platform provides perfectly good C99 support in stdlib.h, but is lacking
C99 support in a single other area (e.g. C99 complex), then that is sufficient to
cripple cstdlib.

I see that that are other, more specialized feature macros like e.g.
_GLIBCXX_USE_C99_MATH.
Why not have _GLIBCXX_USE_C99_STDLIB?
I hope that this suggestion makes sense.

Thank you.
-- 
Andriy Gapon