According to valgrind, there is a memory leak. When fixing that there is a core-dump instead.
Since generate_key is the part that is important for the quality of the key we keep the old
compute_key part to avoid memory leakage.

Re-structure  dh_compute_key_nif and dh_generate_key_nif to see variable scoping and alloc/dealloc pairs better

Not to be used. Uses not yet released functions in OpenSSL 1.1.1-pre8-dev

"curves" in crypto:supports returns list of actually supported ec_curves

This reverts commit fd8e49b5bddceaae803670121b603b5eee8c5c08.