Update: Do not init OpenSSL since 1.1.0

Explicitly initializing the library is not longer needed since
OpenSSL 1.1.0 and the SSL_library_init function is deprecated.

Citing the manual:

> As of version 1.1.0 OpenSSL will automatically allocate all resources
> that it needs so no explicit initialisation is required. Similarly it
> will also automatically deinitialise as required.

Fix #2318

src/tls.c

@@ -56,8 +56,10 @@ struct tls_tag {
 
 void       tls_initialize(void)
 {
+#if OPENSSL_VERSION_NUMBER < 0x10100000L
     SSL_load_error_strings(); /* readable error messages */
     SSL_library_init(); /* initialize library */
+#endif
 }
 void       tls_shutdown(void)
 {