- Replace CHECKs for no_precomp ctx by ARG_CHECKs without a return
- Allow usage of external default callbacks
- Include stdio.h and stdlib.h explicitly in secp256k1.c
- Add secp256k1_ prefix to default callback functions
- Add missing #(un)defines to base-config.h
- cmake build
This is a backport of libsecp256k1 PR595