Add AM_GNU_GETTEXT macros
AM_ICONV relies on config.rpath and autopoint/gettextize will
only copy these in when the AM_GNU_GETTEXT macros are present.

This is needed for the next commit that deletes config.rpath since
it is cruft that should be copied in by autotools not embedded.

Run autopoint to copy in config.rpath and
leave it to automake to copy into the tarball.