Add wolfSSL_EVP_PKEY_paramgen to the compatibility layer.

Currently, it only supports ECC, which is all we need it for for the OpenSplice
port we're working on. In the ECC case, all it needs to do is set the group
appropriately. The logic is very similar to `wolfSSL_EVP_PKEY_keygen`, minus
the final step of actually generating the key.