m4/Makefile.am: inttypes.m4 hasn't been available since gettext-0.15, and since we now require gettext >= 0.17 ... we...

Original commit message from CVS:
* m4/Makefile.am:
inttypes.m4 hasn't been available since gettext-0.15, and since we now
require gettext >= 0.17 ... we can remove it from the list of files to
dist.