Use -listen instead of -nolisten for new Xorg

Newer Xorg versions don't listen to tcp sockets
by default, so instead of explicitly passing
-nolisten to disable tcp sockets by default,
we need to explicitly pass -listen to enable
tcp sockets when DisallowTCP=false.

Older versions don't support the -listen flag,
so we check the version and if it's >= 1.17 then
we specify -listen tcp

Signed-off-by: Nathaniel Roach <nroach44@gmail.com>

https://bugzilla.gnome.org/show_bug.cgi?id=750026