wayland-egl: introduce wayland-egl-backend.pc

File will be installed alongside the backend header.

This way vendor implementations have enough information about the
interface and they can build their backend/driver library accordingly.

Cc: Miguel A. Vico <mvicomoya@nvidia.com>
Cc: James Jones <jajones@nvidia.com>
Cc: Daniel Stone <daniels@collabora.com>
Cc: duncan-roe <duncan_roe@optusnet.com.au>
Cc: Takanari Hayama <taki@igel.co.jp>
Signed-off-by: Emil Velikov <emil.velikov@collabora.com>
Reviewed-by: Miguel A Vico Moya <mvicomoya@nvidia.com>
Reviewed-by: Arnaud Vrac <avrac@freebox.fr>

egl/wayland-egl-backend.pc.in

@@ -0,0 +1,9 @@
+prefix=@prefix@
+exec_prefix=@exec_prefix@
+includedir=@includedir@
+
+Name: wayland-egl-backend
+Description: Backend wayland-egl interface
+Version: 3
+Libs:
+Cflags: -I${includedir}