ssl: prefer TLS_method() over SSLv23_method()

OpenSSL 1.1.0 replaced SSLv23_method() with TLS_method(). SSLv23_method
which still exists in 1.1.0, as a macro around TLS_method, will
eventually be removed. Use the new name if possible.

Author: rhenium

ext/openssl/ossl_ssl.c

@@ -121,7 +121,11 @@ ossl_sslctx_s_alloc(VALUE klass)
     VALUE obj;
 
     obj = TypedData_Wrap_Struct(klass, &ossl_sslctx_type, 0);
+#if OPENSSL_VERSION_NUMBER >= 0x10100000 && !defined(LIBRESSL_VERSION_NUMBER)
+    ctx = SSL_CTX_new(TLS_method());
+#else
     ctx = SSL_CTX_new(SSLv23_method());
+#endif
     if (!ctx) {
         ossl_raise(eSSLError, "SSL_CTX_new");
     }