MacGui: fix a bug when saving a preset, the x264 system is used but the unparsed string is empty (all defaults).



git-svn-id: svn://svn.handbrake.fr/HandBrake/trunk@5387 b64f7644-9d1e-0410-96f1-a4d463321fa5
MacGui: when switching from the x264 system to the advanced panel, populate the advanced panel's options string with the unparsed x264 system options.

Also, don't reset the x264 system widgets, so that the x264 system settings are not lost when switching back.

When loading a preset whic uses the advanced panel, do reset the x264 system widgets, however.



git-svn-id: svn://svn.handbrake.fr/HandBrake/trunk@5388 b64f7644-9d1e-0410-96f1-a4d463321fa5
Update Mac build instructions.



git-svn-id: svn://svn.handbrake.fr/HandBrake/trunk@5389 b64f7644-9d1e-0410-96f1-a4d463321fa5