Replace deprecated cogl_color_set_from_4ub() with cogl_color_init_from_4ub().
Replace cogl_pop/push_matrix() with cogl_framebuffer_pop/push_matrix.

Though this new API needs us to define COGL_ENABLE_EXPERIMENTAL_API
before including cogl/cogl.h and none of the clutter examples or
clutter itself use this - they still use clutter_push_matrix.