MacGui: add getters and setter for x264 preset system.

Simplifies code and makes it more readable.

Also more refactoring, more bugfixes.



git-svn-id: svn://svn.handbrake.fr/HandBrake/trunk@5135 b64f7644-9d1e-0410-96f1-a4d463321fa5
MacGui: cosmetics.



git-svn-id: svn://svn.handbrake.fr/HandBrake/trunk@5136 b64f7644-9d1e-0410-96f1-a4d463321fa5