Remove TLS custom_init() API

src/tls_openssl.c

@@ -28,10 +28,6 @@ void mg_tls_init(struct mg_connection *c, struct mg_tls_opts *opts) {
   if (tls == NULL) {
     mg_error(c, "TLS OOM");
     goto fail;
-  } else if (opts->custom_init != NULL &&
-             opts->custom_init(c, opts, tls) != 0) {
-    mg_error(c, "TLS custom init failed");
-    goto fail;
   }
 
   if (!s_initialised) {