Use shared .pri file for wayland_common and GL integrations

wayland_common.pro missed pkg-config for xkbcommon.
But wayland-common.pri has it. Actually, Both the .pro and the .pri
has many identical configurations. Make it to share
wayland_common_share.pri for those configuations including xkbcommon
to build wayland_common and GL integrations.

Change-Id: I397592eae482976c18d3e86bd8e0427a5f219d06
Reviewed-by: Jørgen Lind <jorgen.lind@digia.com>