* lib/stdalign.in.h (_Alignas): Do not define using __attribute__
if __attribute__ is defined as a macro, as __attribute__ surely a
no-op in that case and this is an area where __attribute__ cannot
simply be ignored.
* m4/stdalign.m4 (gl_STDALIGN_H): Include <stdint.h> so that
it #defines __attribute__(x) to nothing on glibc-based systems
when non-GNU-C-compatible compilers are used.
This exposes a bug in Tiny C Compiler 0.9.27’s implementation
of _Alignas on glibc platforms.