Clean up some of the questions in the FAQ. Namely:
o Convert statements ("I'd like to become a Web mirror") into questions

("How do I become a Web mirror?").

o Properly mark up errors with <errorname> instead of <literal>.

And a minor nit:
o Refer to the X window system as the X window system (instead of "the X

window").

Reviewed by: nik, dd, Arnaud S. Launay <asl@launay.org>