Documentation update broken web addresses

I've found some web addresses not responding, giving the cannot
connect error when trying to load them. The below patch updates
the addresses that are not connecting with the best that I can find,
and also fixes a couple of addresses, so people can either choose an older
version of the package and/or a newer version(i.e. ppp).

Signed-off-by: Justin P. Mattock <justinmattock@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>