WinGui: Change the update checker to use the 64bit appcast when the operating system is 64bit even when the app is the 32bit version.  
Added Operating bit-ness to the log header.

git-svn-id: svn://svn.handbrake.fr/HandBrake/trunk@6392 b64f7644-9d1e-0410-96f1-a4d463321fa5