[SysApps] Make CodecIDToAudioCodec and CodecIDToVideoCodec available as global functions

Make CodecIDToAudioCodec and CodecIDToVideoCodec available as global functions
so that they can be used by Device Capabilities getAVCodecs() interface to
query the list of supported codecs.
Merge pull request #99 from nagineni/devcap_codecs

Make CodecIDToAudioCodec and CodecIDToVideoCodec available as global functions