dshowaudiodec: support AAC and others on Windows 7+

Submitted by Jo Shields

Link to original bug (#665643)

Description

Windows 7 added support for AAC file playback, without needing external codecs - as per http://msdn.microsoft.com/en-us/library/windows/desktop/dd390676%28v=vs.85%29.aspx

It would be nice to add the appropriate new audio subtypes to dshowdecwrapper, such that GStreamer apps on Windows can play AAC files without the usual codec patent license concerns that go along with redistributing faad.