trau-decode: refactor trau-hr-dump The desire is to create a companion program that will read hex lines representing TRAU-8k frames and then decode those frames in exactly the same way how we currently decode frames read from binary capture files. Hence the decoder portion of trau-hr-dump needs to be factored out.

The two little programs in this directory analyze PCM timeslot recordings
that contain Abis/Ater TRAU frames, such as those in ../trau-files directory.
These programs make use of Themyscira GSM codec libraries libgsmfr2 and
libgsmefr.