wxmac: add --without-mediactrl option to disable dependency on QuickTime

QuickTime being 32bit only creates some issues, for example wxHaskell uses `wx-config --libs` output which includes `-framework QuickTime` when building with mediactrl enabled, and then fails to run on 64bit because the library can't be loaded: https://github.com/jodonoghue/wxHaskell/issues/2