This updates the Cogl Pango api to no longer require a default context
and also cleans up the public api a bit.
The CoglPangoRenderer type has been made private to be
consistent with other pango backends where the renderer is merely an
implementation detail.
The drawing apis such as cogl_pango_render_layout where made more
consistent with other pango backend apis so we now have replacements
like cogl_pango_show_layout().
Reviewed-by: Neil Roberts <neil@linux.intel.com>
(cherry picked from commit bba2defe8c08a498b2dcb84bcf5b5a33f16eed27)
Note: API changes were reverting in cherry-picking this patch
579db9083d