gtk+3: Upgrade 3.18.8 -> 3.20.6

gtk+3: Upgrade 3.18.8 -> 3.20.6

* Remove a patch that's no longer needed (as we don't
  have a problem with client side decorations anymore)
* Wayland build now depends on wayland-protocols:
  Use same WAYLAND_PROTOCOLS_SYSROOT_DIR trick as weston so
  protocols are found and multilib build does not break
* Add new binary gtk-query-settings to -dev package
* Rebase patches
* Modify 0003-Add-disable-opengl-configure-option.patch so
  that gdkx.h really is generated whenever it changes

* Depend on wayland-protocols in gtk+3-dev if Wayland is enabled as otherwise
  the pkg-config files can't be used - RB

Signed-off-by: Jussi Kukkonen <jussi.kukkonen@intel.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>
gtk+3: depend on wayland-protocols if wayland enabled