Open SSL 3 test failures

[yeastplume]

Note that when built on a system using openssl 3.0, (more recent arch distros, for instance), the test

run_ecdsa_der_parse on line 4654 of tests.c fails.

I have not looked into the reason, (this function is unused by grin) but we'll likely need to revisit the build when most of the world moves on to openssl 3.