WinGui: Enable the x265 raw muxer for testing.  Note to everyone playing with this. This is highly experimental at this stage. There is no support for audio and the encoder is slow compared to x264. It's still early days.

git-svn-id: svn://svn.handbrake.fr/HandBrake/trunk@6063 b64f7644-9d1e-0410-96f1-a4d463321fa5