tfo/find-is-hdr: move here from freecalypso-reveng This little program was developed in freecalypso-reveng Hg repository in 2023-03, when we didn't have a separate repository for network-side reverse eng, but now that we do have separate repositories for FreeCalypso (mobile side) vs network side reverse eng, move TFO RE work to the proper place.

The two starting source files in this directory (e1_ts2_efr.bin and
e1_ts2_fr.bin) originate from Osmocom:

https://cgit.osmocom.org/libosmo-abis/tree/contrib/trau2rtp

The Makefile contained here automates the process of extracting interesting
bits from these E1 Abis UL recordings.