[build] Build Cogl introspection data

[build] Build Cogl introspection data

Currently, the introspection data for Cogl is built right into
Clutter's own typelib. This makes functions like:

  cogl_path_round_rectangle()

Appear as:

  Clutter.cogl_path_round_rectangle()

It should be possible, instead, to have a Cogl namespace and:

  Cogl.path_round_rectangle()

This means building introspection data for Cogl alone. Unfortunately,
there are three types defined in Cogl that confuse the introspection
scanner, and make it impossible to build a typelib:

  COGLint
  COGLuint
  COGLenum

These three types should go away before 1.0, substituted by int,
unsigned int and proper enumeration types. For this reason, we can
just set up the GIR build and wait until the last moment to create
the typelib. Once that has been done, we will be able to safely
remove the Cogl API from the Clutter GIR and typelib and let
people import Cogl if they want to use the Cogl API via introspection.