Added support to get DH and ECDH parameters

You can know get DH and ECDH parameters used to exchange keys in SSL / TLS sessions.
I use a crappy hack to be able to deal with internal structures used by OpenSSL (I copy some headers after compilation).
When this will be merged, I'll make a pull request to add this support to SSLyze. It'll be able to output (EC)DH group sizes like that:
  * TLSV1_1 Cipher Suites:
      Accepted:                        
                 ECDHE-RSA-AES256-SHA          ECDH-256 bits  256 bits  HTTP 401 Unauthorized              
                 DHE-RSA-CAMELLIA256-SHA       DH-1024 bits   256 bits  HTTP 401 Unauthorized  

I'm sorry I'm not able to test my patches on Windows / Windows64, it should work but I cannot be sure.

I also fix a warning in nassl_BIO.c.