All other private keys are exported in PKCS#8 format, while EC
keys use traditional format. Switch them to use PKCS#8 format as
well.
As the OpenSSL docs say:
> PEM_write_bio_PrivateKey_traditional() writes out a private key
> in the "traditional" format with a simple private key marker and
> should only be used for compatibility with legacy programs.
New features:
- openssl_get_curve_names => list ECC curve names
- generate a ECC public key pair
- generate an CSR with an ECC key
- export x,y,d params of ECC public/private key
Thanks to @bukka for the review and feedback
