Move event polling into CoglRenderer

This updates the cogl_poll_ apis to allow dispatching events before we
have a CoglContext and to also enables pollfd state to be changed in a
more add-hoc way by different Cogl components by replacing the
winsys->get_poll_info with _cogl_poll_renderer_add/remove_fd functions
and a winsys->get_dispatch_timeout vfunc.

One of the intentions here is that applications should be able to run
their mainloop before creating a CoglContext to potentially get events
relating to CoglOutputs.

Reviewed-by: Neil Roberts <neil@linux.intel.com>

(cherry picked from commit 667e58c9cb2662aef5f44e580a9eda42dc8d0176)

cogl/cogl-renderer.c

@@ -168,6 +168,8 @@ _cogl_renderer_free (CoglRenderer *renderer)
                    NULL);
   g_slist_free (renderer->event_filters);
 
+  g_array_free (renderer->poll_fds, TRUE);
+
   g_free (renderer);
 }
 
@@ -181,6 +183,8 @@ cogl_renderer_new (void)
   renderer->connected = FALSE;
   renderer->event_filters = NULL;
 
+  renderer->poll_fds = g_array_new (FALSE, TRUE, sizeof (CoglPollFD));
+
 #ifdef COGL_HAS_XLIB_SUPPORT
   renderer->xlib_enable_event_retrieval = TRUE;
 #endif