[master clock] Fix MT safety issues
[master clock] Fix MT safety issues

Fix MT issues when enabling threading in Clutter.

Fixes bug:

  http://bugzilla.openedhand.com/show_bug.cgi?id=1655

Signed-off-by: Emmanuele Bassi <049ee2061f71220e5aaf33f5be422fc2a2b06a44@linux.intel.com>

jigpu/clutter,Distrotech/clutter,heysion/clutter-clone,jigpu/clutter,ebassi/clutter,djdeath/clutter,djdeath/clutter-android,spatulasnout/clutter,dlespiau/clutter,rkudiyarov/clutter_osx,Distrotech/clutter,kerrickstaley/clutter-vala,spatulasnout/clutter,collects/clutter,nobled/clutter,djdeath/clutter-multithreaded,djdeath/clutter-android,ebassi/clutter,rkudiyarov/clutter_osx,rkudiyarov/clutter_osx,dlespiau/clutter,djdeath/clutter-multithreaded,collects/clutter,tardyp/clutter,spatulasnout/clutter,djdeath/clutter-multithreaded,jigpu/clutter,spatulasnout/clutter,djdeath/clutter-android,jigpu/clutter,GNOME/clutter,GNOME/clutter,dlespiau/clutter,collects/clutter,collects/clutter,ebassi/clutter,kerrickstaley/clutter-vala,djdeath/clutter-android,jigpu/clutter,kerrickstaley/clutter-vala,djdeath/clutter-multithreaded,djdeath/clutter,tardyp/clutter,jigpu/clutter,heysion/clutter-clone,ebassi/clutter,Distrotech/clutter,ebassi/clutter,GNOME/clutter,GNOME/clutter,nobled/clutter,djdeath/clutter-android,collects/clutter,heysion/clutter-clone,Distrotech/clutter,djdeath/clutter,nobled/clutter,kerrickstaley/clutter-vala,spatulasnout/clutter,heysion/clutter-clone,djdeath/clutter,tardyp/clutter,Distrotech/clutter,GNOME/clutter,djdeath/clutter,djdeath/clutter,heysion/clutter-clone,rkudiyarov/clutter_osx,Distrotech/clutter