To allow us to have gobject properties that accept a CoglMatrix value we
need to register a GType. This adds a cogl_gtype_matrix_get_type function
that will register a static boxed type called "CoglMatrix".
This adds a new section to the reference manual for GType integration
functions.
So we can keep track of the experimental progress of Cogl 2.0 features
this adds a standalone Cogl 2.0 Reference Manual which doesn't cover
the deprecated 1.x symbols and removes the need for a "Cogl
experimental API" chapter since those sections now make up the main
table of contents.