X11: Provide specific X error when SDL_GL_CreateContext fails.

This makes the X error handler used for GL context creation handle *all* errors
and provide the user with specific error messages when SDL_GL_CreateContext
fails.

CR: icculus@icculus.org
SDL_opengl: Move glext.h to a separate file.

--HG--
extra : rebase_source : 36b782051e621861bfc8f47249a4e2d1ea8f4775
SDL_opengles2: Separate out GLES2 headers.

--HG--
extra : rebase_source : 67a615ceb77389a2be5ba5177966e3255bdc964b
SDL_opengl: Update to glext.h from Khronos dated 2014-05-21.

This updates to the latest glext.h from Khorons that includes the OpenGL
4.4 specification. It was retrieved from
http://www.opengl.org/registry/api/GL/glext.h at 2014-06-04.

--HG--
extra : rebase_source : 85adb5e14c704f0202041dc0dd9ef9402508f1f6
SDL_opengles2: Update to latest Khronos headers.

This updates to the latest Khronos headers, which gives the latest
headers for MSVC.

The following files were retrieved on 2014-06-04:

http://www.khronos.org/registry/gles/api/GLES2/gl2.h
http://www.khronos.org/registry/gles/api/GLES2/gl2ext.h
http://www.khronos.org/registry/gles/api/GLES2/gl2platform.h
http://www.khronos.org/registry/egl/api/KHR/khrplatform.h

And they were modified to not include each other themselves.

--HG--
extra : rebase_source : 99ed4a21b67a35a11f9af80de79d844ea8ac0d80
Fixed escape cancelling fullscreen mode now that the SDL window is the first res
ponder.
Wait for the fullscreen transition to complete before allowing the application to continue.
This fixes Alt-Enter in the Steam streaming client, which sets the window size and position immediately after switching out of fullscreen mode.
SDL_opengl: Fix Mac build with new glext.h
SDL_opengl: Fix Mac build for SDK 10.9 too.
Added a hint to disable window frame and title bar interaction when the cursor is hidden
Added a hint to disable windows message processing in SDL_PumpEvents()
SDL_SetHint( SDL_HINT_WINDOWS_ENABLE_MESSAGELOOP, "0" );
Added an API function to warp the mouse cursor in global screen space: SDL_WarpMouseGlobal()
Fixed Mac OS X build
Fixed bug where changing the window border would change the window size on Windows.
When the window fullscreen mode changes, update the display resolution
Fixed bug 2526, but regressed delivering dead key presses
Added annotations to help code analysis tools

CR: Bruce Dawson
Ryan C. Gordon <icculus@icculus.org> 2014-05-24 01:23 -0400
Generated dynapi stuff for the new WinRT entry points.
http://hg.libsdl.org/SDL/rev/6a9da341d3e8
Fixed crash and lost pixel data when recovering from a lost device situation (e.g. alt-tab from fullscreen)
Setting the window size changes the fullscreen display mode, unless a window display mode has been set.

Testing:
* Ran testsprite2 --fullscreen, used Ctrl+ and Ctrl- to change window sizes, verified that the display mode changed as well.