When a client binds an incompatible version, we should terminate it.
This check should only be there for the unstable version, as once it is
declared stable and renamed, future versions will be backward compatible.
https://bugzilla.gnome.org/show_bug.cgi?id=753855
The global wl_pointer_gestures object is now created, effectively
bridging pinch/swipe gestures with clients, so they're now
accessible to clients implementing the protocol.