aix: Fix _STDC_FORMAT_MACROS in inttypes.h [PR97044]

aix: Fix _STDC_FORMAT_MACROS in inttypes.h [PR97044]

AIX protects the STDC Format Macros in a manner that can prevent the
definition of the macros depending on the order of header inclusion.

The protection of the macros was referenced in C99, removed in C11, and
never specified in any C++ standard. Also, the macros are in the namespace
reserved to the implementation (compiler) so the compiler is permitted to
choose to inject those names.

fixincludes/ChangeLog:

2020-09-17  David Edelsohn  <dje.gcc@gmail.com>

	PR target/97044
	* inclhack.def (aix_inttypes): New fix.
	* fixincl.x: Regenerate.
	* tests/base/sys/inttypes.h: New file.