MacGui: fix a bug where the iPod 5G checkbox would be disabled for x264 in MP4.

This would happen when switching from MKV with a Theora encoder to MP4: the encoder would be reset to x264, but we failed to detect the change of encoder and therefore didn't call videoEncoderPopUpChanged.

Also, don't needlessly call twoPassCheckboxChanged after videoEncoderPopUpChanged since the latter calls the former.



git-svn-id: svn://svn.handbrake.fr/HandBrake/trunk@5452 b64f7644-9d1e-0410-96f1-a4d463321fa5