Add Makefile target update-secp256k1, and run it. The only API change is that len is now an IN-OUT parameter to serialization functions. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Imported from: git@github.com:sipa/secp256k1.git schnorr3 (0ab0b47) Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>