X.man: update program lists/info for modern era

We no longer have a monolithic X.Org distribution, nor a separate
user-contributed distribution from X.Org, but instead many OS distros.

Also stop recommending so much abandonware, but do point out the programs
we've added over the years and still maintain.

Signed-off-by: Alan Coopersmith <alan.coopersmith@oracle.com>
Reviewed-by: Jeremy Huddleston Sequoia <jeremyhu@apple.com>