www/elinks: Fix build on OpenSSL 1.1.1

Use the provided getter routine instead of directly accessing the contents
of the SSL struct, which is no longer exported as part of the ABI.

Reviewed by:	beat@
Approved by:	beat@
Differential Revision:	https://reviews.freebsd.org/D18325

www/elinks/files/patch-src_network_ssl_socket.c

@@ -9,3 +9,12 @@
  #elif defined(CONFIG_GNUTLS)
  	{
  		/* GnuTLS does not support SSLv2 because it is "insecure".
+@@ -145,7 +145,7 @@
+ 		}
+ 
+ 		if (client_cert) {
+-			SSL_CTX *ctx = ((SSL *) socket->ssl)->ctx;
++			SSL_CTX *ctx = SSL_get_SSL_CTX(socket->ssl);
+ 
+ 			SSL_CTX_use_certificate_chain_file(ctx, client_cert);
+ 			SSL_CTX_use_PrivateKey_file(ctx, client_cert,