Add the patchset for Wayland EGL support on VideoCore

The VideoCore driver requires an additional patchset to support the
Wayland EGL platform. The platform is a necessity for adding AC support
to WebKitGTK+ under Wayland.
Wayland EGL version in wayland-egl.pc should be 10

The version of the Wayland EGL support should equal the version of EGL,
which is 10. The version should be hard-coded in wayland-egl.pc.in, just
like it is hard-coded in egl.pc.in.
Build rpi-userland in release mode, with Wayland

Two additional macros should be listed in the cmake invocation,
one to enable the release build (which avoids hopefully hurtless
assertions) and one to enable building Wayland EGL platform.
Update Cairo version, enable cairo-egl on Wayland

Bump the Cairo version to 1.12.16. cairo-egl is enabled when building for Wayland.
Enable EGL clients for Weston when building the RPi backend

The (simple) EGL clients should be enabled when building the RPi backend of Weston.
They should also be installable so they can be tested out on target hardware.
weston-launch is also enabled and the Cairo image backend is explicitly demanded.
Merge pull request #10 from zdobersek/wayland-egl-platform

Wayland egl platform