WinGui: Disable Custom Anamorphic calculations (Will implement these via libhb after the next release) but leave the options as passthru only.  Hide the Keep AR checkbox when it's not applicable. 

git-svn-id: svn://svn.handbrake.fr/HandBrake/trunk@5406 b64f7644-9d1e-0410-96f1-a4d463321fa5