strtoimax: eliminate need for stdint.h, inttypes.h checks

strtoimax: eliminate need for stdint.h, inttypes.h checks

* m4/strtoimax.m4 (gl_FUNC_STRTOIMAX): Don't use
gl_AC_HEADER_STDINT_H or gl_AC_HEADER_INTTYPES_H.  This reduces
the prerequisites for a recently-introduced strtoimax test.
I guess this might cause strtoimax to be replaced when not
strictly necessary on older hosts, but this shouldn't introduce
any bugs and it should make Emacs 'configure' faster on typical
modern hosts.  Problem discovered when importing the latest gnulib
to an Emacs test version.
* modules/strtoimax (Files): Remove m4/stdint_h.m4, m4/inttypes_h.m4.