Fix typo
Merge pull request #2335 from petertodd/readme-typo

Minor: Fix typo in README.md
Add speedup for sig verification based on secp256k1.
Some optimizations for Hal's secp256k1 verifier
Precalculate P, N and G*lambda in CSecp256k1Consts
Refactor secp256k1 ECDSA verify code to mimic generic version
Allow verification of optimized secp256k1 code
Implement Hal's suggestion for a faster G split
Build test objects separately
Precompute multiples of G
Make optimized secp256k1 optional