[Cryptech Core] Pavel's ECDSA cores are working

[Rob Austein]

I now have a working test build with both of Pavel's ECDSA base point
multiplier cores (ECDSA256 and ECDSA384) and ARM software to use them.
ECDSA signature time is better than an order of magnitude faster with
these cores than doing everything in software (numbers are still a bit
fuzzy, testing continues).

Unless somebody strongly objects, soon, I will promote these to:

  core/pkey/ecdsa256/
  core/pkey/ecdsa384/

and the common code to:

  core/math/ecdsalib/

and will merge the core_config_cleanup branches in core/platform/* to
master, then generate new binary packages.