vendor: Mega update all dependencies

GitHub-Pull-Request: https://github.com/syncthing/syncthing/pull/4080

vendor/github.com/golang/snappy/decode_amd64.go

@@ -2,6 +2,10 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+// +build !appengine
+// +build gc
+// +build !noasm
+
 package snappy
 
 // decode has the same semantics as in decode_other.go.