OpenSSL: fix ECC support build-time check
OpenSSL: fix ECC support build-time check

With at least OpenSSL 1.1.0, checking the header is not enough. OpenSSL
does provide a way to check it directly though.

Fixes compilation without ECC support.

sartura/libwebsockets,sartura/libwebsockets,sartura/libwebsockets,sartura/libwebsockets,sartura/libwebsockets,sartura/libwebsockets,sartura/libwebsockets