Log Message:
Update clutter-gst to 2.0.8.
while here, enable introspection optin by default.

clutter-gst 2.0.8 (18/09/2013)
===============================================================================

List of changes since 2.0.6

 o Fix a crash in ClutterGstPlayer when disposing instances too fast

 o Fix a crash in ClutterGstVideoSink

 o Fix a crash in ClutterGstVideoSink when running on Wayland with X11
   backend compiled

Many Thanks to:

    Thomas Wood

clutter-gst 2.0.6 (24/05/2013)
===============================================================================

List of changes since 2.0.4

 o Fix a bug when subclassing ClutterGstPlayer class

 o Add support of X11 pixmap as video texture when decoding with
   Gstreamer-vaapi

Many Thanks to:

    Gwenole Beauchesne
    Sjoerd Simons