Assorted minor corrections
Summary:
- Add check that restrict pointers don't alias with all parameters.
- clean dependendies in field_*_impl.h
- Correct math typos in field_*.h
This is a backport of secp256k1's PR539
Test Plan:
ninja check-secp256k1
Reviewers: #bitcoin_abc, Fabien
Reviewed By: #bitcoin_abc, Fabien
Differential Revision: https://reviews.bitcoinabc.org/D4975