applemedia: support public version of CoreMedia

applemedia: support public version of CoreMedia

Also rename the relevant API so we mirror the public API more closely, and
switch to CoreFoundation CFTypeRef style typedefs. We still support the old
private CoreMedia in order to not break OS X support.

This means that vtenc and vtdec are now compatible with iOS 4.x, and in
theory also future versions of OS X, where this API may turn public like
it has on iOS.