Fix ssl ecc handshake crash on unknown curve

original message at http://erlang.org/pipermail/erlang-questions/2014-March/078083.html

When buggy client or security scanner opens a connection to OTP ssl server and sends Supported Elliptic Curves Client Hello Extension with '0' or any other curve id not defined in tls_v1:enum_to_oid/1, a server crashes.

This pull requests fixes this problem by ignoring unknown curve ids.