Revert "Bug 941296 - Add wrappers for system CoreMedia framework. r=cpeace,ted"

This reverts commit 4ef0dfd16df71bf061b29155110316a017cf11fb.

Conflicts:
	content/media/fmp4/moz.build
Bug 941296 - Check for CoreMedia headers in configure. r=ted

We need to build against the CoreMedia framework headers which
are only available on 10.7 and later, although we run on 10.6.

Check that this framework is available an configure time and
print a relevant error message in case someone passes
--with-macos-sdk=/Developer/SDKs/MacOSX10.6.sdk.
Bug 1045128 - Bump MacOS X SDK to 10.7 for release builds. r=ted