Add cipher aliases for DHE (the correct name for EDH) and ECDHE (the
correct name for EECDH). The EDH and EECDH aliases remain for backwards
compatibility.
Only require an EC public key in tls1_set_ec_id(), if we need to provide
a compression identifier. In the case of a server using ephemeral EC keys,
the supplied key is unlikely to have a public key where
SSL_CTX_set_tmp_ecdh() is called after SSL_OP_SINGLE_ECDH_USE has been
set. This makes ECDHE ciphers work again for this use case.