Feature #1568: Move various code bits to libosmocore
GSM 05.03 code migration to libosmogsm
There is a lot of code related to GSM L1 should be migrated from OsmoBTS
to libosmogsm. The reason is that it would be better to have one shared
implementation of the convolutional codes, mapping, interleaving, etc.,
because then in near future it can be used not only from OsmoBTS, but
also from OsmocomBB and even from foreign projects, such as GR-GSM.