gettext: Add config.rpath and Makefile.in.in to gettext-minimal-native

We need gettext-minimal-native to be able to install config.rpath and
Makefile.in.in so that we don't get version mismatch errors when subsequently
using the reconfigured software.

This patch moves the two files to be provided by minimal-native so
that we can better 'gettextize' software without needing the full
gettext-native when using --disable-nls.

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>