Added a feature to use accelerometer data to rotate camera view in software
when the camera is physically rotated such that the view on the screen is
always upright even when the camera is upside down. Enabling it, and
disabling it is done with the "r" key. Not on by default. I enabled several
things that were disabled in the last patch, but only when rotation
mode is toggled on.

I uploaded a youtube video of this feature
http://www.youtube.com/watch?v=JSjV1Y1eC8M

Signed-off-by: Daniel Patrick Johnson <teknotus@gmail.com> (teknotus)
Merge branch 'master' of git://github.com/teknotus/libfreenect

Conflicts:
	examples/glview.c

Use the 'o' key in glview to rotate video with accelerometer - fixes #234

Reviewed-by: Benn Snyder <benn.snyder@gmail.com>