applemedia: don't use the dynamic API for public frameworks

applemedia: don't use the dynamic API for public frameworks

Public frameworks don't need to build the API dynamically, we instead
use the framework directly.
The exception is for VideoToolbox which went public in the 10.8 SDK,
but it's still private in older version of the SDK and iOS. This allow
building the plugin against SDK's where it's not a public framework.