Wayland support

Based on the original port to Wayland by: Joel Teichroeb, Benjamin Franzke, Scott Moreau, et al.

Additional changes in this commit, done by me:

* Wayland uses the common EGL framework
* EGL can now create a desktop OpenGL context
* testgl2 loads GL functions dynamically, no need to link to libGL anymore
* Assorted fixes to the Wayland backend

Tested on the Weston Compositor (v1.0.5) that ships with Ubuntu 13.10,
running Weston under X. Tests ran: testrendercopyex (all backends), testgl2, testgles2,testintersections

cmake/sdlchecks.cmake

@@ -505,6 +505,29 @@ macro(CheckX11)
   endif(VIDEO_X11)
 endmacro(CheckX11)
 
+# Requires:
+# - EGL
+macro(CheckWayland)
+  if(VIDEO_WAYLAND)
+    pkg_check_modules(WAYLAND wayland-client wayland-cursor wayland-egl egl xkbcommon)
+    if(WAYLAND_FOUND)
+      link_directories(
+          ${WAYLAND_LIBRARY_DIRS}
+      )
+      include_directories(
+          ${WAYLAND_INCLUDE_DIRS}
+      )
+      set(EXTRA_LIBS ${WAYLAND_LIBRARIES} ${EXTRA_LIBS})
+      set(HAVE_VIDEO_WAYLAND TRUE)
+      set(HAVE_SDL_VIDEO TRUE)
+
+      file(GLOB WAYLAND_SOURCES ${SDL2_SOURCE_DIR}/src/video/wayland/*.c)
+      set(SOURCE_FILES ${SOURCE_FILES} ${WAYLAND_SOURCES})
+      set(SDL_VIDEO_DRIVER_WAYLAND 1)
+    endif(WAYLAND_FOUND)
+  endif(VIDEO_WAYLAND)
+endmacro(CheckWayland)
+
 # Requires:
 # - n/a
 #