Making it possible to define the elliptic curve by name for ephemeral Diffie–Hellman.

Motivation:

Improving security of SSL transactions that use ECDHE-based ciphers.

Modifications:

Adding a new native operation on OpenSSL that makes it possible to set
the elliptic curve by merely giving its name. An exception is thrown in
case the curve is not found or fails to load.

Result:

One can now setup her/his elliptic curve as can be chosen in the list
generated by:
openssl ecparam -list_curves
This is done e.g. by calling:
SSLContext.setTmpECDHByCurveName(sslContext.context(), "secp256k1")
Note that prime256v1 is the default value.
corrected issue 5
Merge branch '1.1.30' into dev

Conflicts:
	src/main/c/sslcontext.c