xfsprogs: add mount options to xfs.5 manpage

xfsprogs: add mount options to xfs.5 manpage

This is a straight cut and paste from the util-linux
mount manpage to xfs.5.

It's pretty much impossible for util-linux to keep up
with every filesystem out there, and Karel has more than
once expressed a wish that mount options move into fs-specific
manpages.

So, here we go.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>