s/_CG_RETURN_[VAL]IF_FAIL/c_return_[val]if_fail()/

Just to be a tiny bit more consistent across cogl and rig we will aim to
use clib utilities where applicable.
clib: Add Red Black Tree api
rbtree: use c_malloc/c_free
rut: add api to request new interface ids
Use C_BEGIN/END_DECLS macro under rut/ and rig/
cogl: s/cg_context/cg_device/
cogl-pango: s/cg_context/cg_device/
cogl-gst: s/cg_context/cg_device/
cogl-path: s/cg_context/cg_device/
cogl-examples: s/cg_context/cg_device/
test-fixtures: s/cg_context/cg_device/
rut: s/cg_context/cg_device/
rig: s/cg_context/cg_device/
tools: s/cg_context/cg_device/
conform: s/cg_context/cg_device/
micro-perf: s/cg_context/cg_device/
device: add cg_device_connect()
Add initial RigText component

UI text used to be handled by RutText but now the aim is to handle
text rendering and layouting more directly in Rig.
stash: markup stuff