Added two stream descriptors that are both used to tell the output
format. If it is not given, the packager will use the output file
extension to determine the output format.
Change-Id: Ib8d5dcf52956c2d451e77ea6a90d9502d4a77064
If a stream has no language metadata, or has the wrong metadata, this
field allows the user to override this on the command-line.
This also maps all specified languages on the command-line to ISO-639-2
tags as required by the MP4 muxer, so that ISO-639-1 tags specified on
the command-line do not cause a DCHECK to fail.
b/18613148
Change-Id: I473baeecbb3d388db5e06d080179ec6a332b4794