update default -rpcsslciphers to include TLSv1.2

- this extends the accepted ciphersuites with TLSv1.2 ones
- also removes !AH, as I could not find documentation on it and the change
  did not result in a changed ciphersuite list (checked via openssl
  ciphers -v)
- closes #3096 (which also contains more details)

src/bitcoinrpc.cpp

@@ -809,7 +809,7 @@ void StartRPCThreads()
         if (filesystem::exists(pathPKFile)) rpc_ssl_context->use_private_key_file(pathPKFile.string(), ssl::context::pem);
         else LogPrintf("ThreadRPCServer ERROR: missing server private key file %s\n", pathPKFile.string().c_str());
 
-        string strCiphers = GetArg("-rpcsslciphers", "TLSv1+HIGH:!SSLv2:!aNULL:!eNULL:!AH:!3DES:@STRENGTH");
+        string strCiphers = GetArg("-rpcsslciphers", "TLSv1.2+HIGH:TLSv1+HIGH:!SSLv2:!aNULL:!eNULL:!3DES:@STRENGTH");
         SSL_CTX_set_cipher_list(rpc_ssl_context->impl(), strCiphers.c_str());
     }