libfrog: move all the userspace support stuff into a new library

libfrog: move all the userspace support stuff into a new library

This library is meant to contain all the Funny Random Other Gunk that
the xfsprogs utilities rely on.  Move all that stuff into this library
to reduce the pollution in the other libraries.

Ribbit!  Ribbit!

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: Eric Sandeen <sandeen@sandeen.net>