Make the compositor test build

Change-Id: Ic4137ff7f69b293db60fa1232602cd4560497d6e
Reviewed-by: Robin Burchell <robin+qt@viroteck.net>
Fix build with Wayland <= 1.1

Change-Id: Idd12c0db73203daa008d93c0dc8053e25dff09e2
Reviewed-by: Jørgen Lind <jorgen.lind@digia.com>
Strip custom prefix from interface name

Interface names for some protocols might not start with wl_ or qt_,
with this change users can specify a prefix of their liking.

Change-Id: I70d40985165c49114b525bdec2a872aa5b0dad6d
Reviewed-by: Jørgen Lind <jorgen.lind@digia.com>