build-sys: Use po4a for manpage translations

build-sys: Use po4a for manpage translations

Using the newer po4a tool for manpage translations. Also removing
the manpage po file update from dist target because it should be
something the is explicitly done.

The git repository will hold the original man pages and the
po translation files. The distribution tarball will hold those
and the translated manpages. This means most people won't need po4a
as the distribution fill will have these translated manpages.