RFC: libosmocore generic CRC

[Sylvain Munaut]

Hi,

I've just pused in libosmocore a branch sylvain/crc with a proposal
for some generic CRC function.

The goal here is to provide a base implementation so that channel
coding/decoding of the various other projects can use this as a base
rather than reimplement their own for each poly. The API is targeted
towards that use (using array of ubit_t rather than a buffer of packed
bits).

The code is generated from a template and expanded into a 8 / 16 / 32
/ 64 bits version by the Makefile (each capable of supporting any crc
length inferior or equal to that. So a CRC12 would use the 16bits
state function).

Appropriate doxygen doc is included.

If nobody has objection / comments / ... I'll go ahead and merge it.

Cheers,

    Sylvain