[Intel-gfx] Fix graphics memory leak on moblin

[Shuang He]

[PATCH] Buffers created for fb should be released when destroy drawable
[PATCH] glXReleaseTexImageEXT should release reference to storage for 
the pixmap
Those two patches are part of fix for memory leak on moblin. There's 
still one issue left in clutter, that:
    According to GLX 1.4 spec, "however, GLXPixmaps created by calls 
other than glXCreateGLXPixmap should not be passed to 
glXDestroyGLXPixmap", so clutter should use glxDestroyPixmap instead of 
glXDestroyGLXPixmap, since their pixmap is created by calling 
glXCreatePixmap.

Thanks
    --Shuang