Upgrade versions of vendored libs

vendor/github.com/DataDog/zstd/zstd_fast.h

@@ -1,5 +1,6 @@
+#ifndef USE_EXTERNAL_ZSTD
 /*
- * Copyright (c) 2016-present, Yann Collet, Facebook, Inc.
+ * Copyright (c) Yann Collet, Facebook, Inc.
  * All rights reserved.
  *
  * This source code is licensed under both the BSD-style license (found in the
@@ -35,3 +36,5 @@ size_t ZSTD_compressBlock_fast_extDict(
 #endif
 
 #endif /* ZSTD_FAST_H */
+
+#endif /* USE_EXTERNAL_ZSTD */