gengenrtl needs to link with libintl

[DJ Delorie]

> > > Thus, I think we should undefine ENABLE_NLS rather than HAVE_LIBINTL_H
> > > to disable NLS when building generator files.  However, configure for
> > > libiberty needs to be modified to add an `--enable-nls' option.

FYI libiberty has no support for HAVE_LIBINTL_H in configure.  Doesn't
even test for it.  Unless some magic is going on behind my back,
--enable-nls is not needed because it would never do anything.

However, I've got a mini-merge for the ENABLE_NLS support in the *.c
files which I'll check in shortly.