This includes the https://github.com/ElementsProject/secp256k1-zkp library
(which is a fork from sipa/secp256k1 used in Bitcoin Core) as a module. It
is currently not used in any app.
This commit the first step towards integrating Liquid (tracking issue #282).
Note that this creates a new 64 kiB read-only data section in .flash2 for
pre-computed tables (secp256k1_ecmult_static_context) which speed up
signature creation and related private key operations.
Co-authored-by: Roman Zeyde <me@romanzey.de>
Co-authored-by: Andrew Poelstra <apoelstra@wpsoftware.net>
Co-authored-by: Pavol Rusnak <pavol@rusnak.io>
