libstdc++: Avoid use of naked int32_t in unseq_backend_simd.h, PR108672

libstdc++: Avoid use of naked int32_t in unseq_backend_simd.h, PR108672

The use of a "naked" int32_t (i.e. without a fitting #include:
stdint.h or cstdint or inttypes.h or an equivalent internal header),
in libstdc++-v3/include/pstl/unseq_backend_simd.h, caused an error for
cris-elf and apparently pru-elf and I guess all "newlib targets".
(Unfortunately, there's a lack of other *-elf targets in recent months
of gcc-testresults archives.)

This does not manifest on e.g. native x86_64-pc-linux-gnu, because
there, a definition is included as an effect of including stdlib.h in
cstdlib (following the trace in native xtreme-header-2_a.ii with
glibc-2.31-13+deb11u5).  Maybe better than chasing the right #includes
is to directly use the built-in type, like so:

libstdc++-v3:

	PR libstdc++/108672
	* include/pstl/unseq_backend_simd.h (__simd_or): Use __INT32_TYPE__
	instead of int32_t.