Added mouse support.

Some applications, depend on the video backend to handle mouse cursors
(namely, hiding them and setting custom ones). Without it they crash.
It should be possible to support this in the wayland backend.

Implemented support for both system and custom cursors using shm.

Fixes Issue #3
Implement GetSysWMInfo hook for wayland.

SDL video backends have a GetSysWMInfo hook to expose window system specific structures to clients that might want to use them. We should expose the following in case clients want to use functionality which SDL does not
provide a suitable abstraction for, eg:

    wl_display
    wl_surface
    wl_shell_surface

Fixes Issue #4
Set the EGL_OPENGL_ES_2_BIT for --enable-video-opengles

Currently, the SDL backend just creates a GL-api EGLContext. We should use
EGL_OPENGL_ES_API when in OpenGL|ES mode.

Fixes Issue #5
Merge branch 'wayland.fix_3' of https://github.com/smspillaz/SDL into wayland
Merge branch 'wayland.fix_4' of https://github.com/smspillaz/SDL into wayland
Merge branch 'wayland.fix_5' of https://github.com/smspillaz/SDL into wayland