* clutter/cogl/gl/cogl-texture.c (cogl_texture_new_from_foreign,
(_cogl_texture_quad_hw, cogl_texture_polygon),
(_cogl_texture_quad_sw): Support GL_ARB_texture_rectangle textures
* clutter/glx/clutter-glx-texture-pixmap.c: Use rectangle textures
when NPOTs are not available or it is forced by the
CLUTTER_PIXMAP_TEXTURE_RECTANGLE environment variable.
* clutter/cogl/gl/cogl.c (cogl_enable): Allow enabling
GL_TEXTURE_RECTANGLE_ARB.