Fix non-standard device orientation values

Yaw and roll were mixed up. Previously 'roll' was assigned to 'alpha'
and 'yaw' was assigned to 'gamma'. Fixed to assign 'yaw' to 'alpha' and
'roll' to 'gamma', matching the standard behavior with Safari iOS 7.1 on
iPhone and Chrome for Android 4.4.
Add support for cancelAnimationFrame

Necessary for Construct 2 support.
Merge pull request #372 from AshleyScirra/c2

Fix non-standard device orientation values & add cancelAnimationFrame
Merge branch 'master' of git://github.com/phoboslab/Ejecta