[cogl] Removes the cogl-current-matrix abstraction

The indirection through this API isn't necessary since we no longer
arbitrate between the OpenGL matrix API and Cogl's client side API.  Also it
doesn't help to maintain an OpenGL style matrix mode API for internal use
since it's awkward to keep restoring the MODELVIEW mode and easy enough to
directly work with the matrix stacks of interest.

This replaces use of the _cogl_current_matrix API with direct use of the
_cogl_matrix_stack API.  All the unused cogl_current_matrix API is removed
and the matrix utility code left in cogl-current-matrix.c was moved to
cogl.c.

doc/reference/cogl/Makefile.am

@@ -57,7 +57,6 @@ IGNORE_HFILES=\
         cogl-defines-gles.h \
 	cogl-internal.h \
 	cogl-material-private.h \
-	cogl-current-matrix.h \
 	cogl-bitmap-private.h \
 	cogl-blend-string.h \
 	cogl-vertex-buffer-private.h \