MacGui: use a shorter NSString method to remove the prefix from the bsdName, as reported by denisx on irc, in HBDVDDetector and and a boxing expression to convert a c string to NSString.

git-svn-id: svn://svn.handbrake.fr/HandBrake/trunk@6275 b64f7644-9d1e-0410-96f1-a4d463321fa5