wayland: install wayland compositor headers + pkgconfig file
wayland: install wayland compositor headers + pkgconfig file

If wayland compositor support has been enabled then we make sure to
install the corresponding public headers and a
clutter-wayland-compositor.pc pkgconfig file.

Reviewed-by: Neil Roberts <822ec91a7ef82248fd36162ca8ac3283eba70848@linux.intel.com>
Reviewed-by: Emmanuele Bassi <049ee2061f71220e5aaf33f5be422fc2a2b06a44@linux.intel.com>

Distrotech/clutter,kerrickstaley/clutter-vala,heysion/clutter-clone,djdeath/clutter,jigpu/clutter,heysion/clutter-clone,jigpu/clutter,jigpu/clutter,djdeath/clutter-android,kerrickstaley/clutter-vala,GNOME/clutter,djdeath/clutter-multithreaded,djdeath/clutter,djdeath/clutter-android,kerrickstaley/clutter-vala,djdeath/clutter-android,GNOME/clutter,djdeath/clutter,djdeath/clutter-android,djdeath/clutter-multithreaded,djdeath/clutter-android,ebassi/clutter,kerrickstaley/clutter-vala,djdeath/clutter-multithreaded,jigpu/clutter,collects/clutter,djdeath/clutter,heysion/clutter-clone,Distrotech/clutter,heysion/clutter-clone,ebassi/clutter,Distrotech/clutter,collects/clutter,collects/clutter,heysion/clutter-clone,djdeath/clutter,ebassi/clutter,GNOME/clutter,GNOME/clutter,jigpu/clutter,jigpu/clutter,ebassi/clutter,Distrotech/clutter,djdeath/clutter-multithreaded,GNOME/clutter,djdeath/clutter,Distrotech/clutter,collects/clutter,ebassi/clutter,collects/clutter,Distrotech/clutter