Applied 'final patch' from bug #874

	Applied 'final patch' from bug #874

	* clutter/cogl/gles/cogl.c:
	* clutter/cogl/gl/cogl.c: The clip planes are now set using the
	inverse projection matrix as the modelview matrix so that they can
	be specified in screen coordinates.

	* clutter/cogl/gles/cogl-context.h (CoglContext):
	* clutter/cogl/gl/cogl-context.h (CoglContext): Added a member to
	cache the inverse projection matrix

	* clutter/clutter-fixed.h: Added a constant for converting from
	radians to degrees.

	* clutter/clutter-fixed.c (clutter_atani, clutter_atan2i): Added
	fixed-point versions of atan and atan2.

	* tests/test-clip.c: Added a test for clipping with various
	rotations and depths.

	* tests/Makefile.am (noinst_PROGRAMS): Added test-clip