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

CMakeLists.txt

@@ -218,6 +218,7 @@ set_option(RPATH               "Use an rpath when linking SDL" ${UNIX_SYS})
 set_option(CLOCK_GETTIME       "Use clock_gettime() instead of gettimeofday()" OFF)
 set_option(INPUT_TSLIB         "Use the Touchscreen library for input" ${UNIX_SYS})
 set_option(VIDEO_X11           "Use X11 video driver" ${UNIX_SYS})
+set_option(VIDEO_WAYLAND       "Use Wayland video driver" ${UNIX_SYS})
 dep_option(X11_SHARED          "Dynamically load X11 support" ON "VIDEO_X11" OFF)
 set(SDL_X11_OPTIONS Xcursor Xinerama XInput Xrandr Xscrnsaver XShape Xvm)
 foreach(_SUB ${SDL_X11_OPTIONS})
@@ -641,6 +642,7 @@ if(UNIX AND NOT APPLE)
     CheckDirectFB()
     CheckOpenGLX11()
     CheckOpenGLESX11()
+    CheckWayland()
   endif(SDL_VIDEO)
 
   if(LINUX)