golang: v↑ go1.16 (1.16.10 -> 1.16.13)

Going Go1.16.10 -> Go1.16.13 brings in fixes to compiler, runtime and stdlib
including security fixes to syscall and net/http packages.

https://go.dev/doc/devel/release#go1.16.minor

Tested manually via adjusted helloworld because nothing intree currently uses Go1.16.

component/golang/buildout.cfg

@@ -59,8 +59,8 @@ environment-extra =
 
 [golang1.16]
 <= golang-common
-url = https://golang.org/dl/go1.16.10.src.tar.gz
-md5sum = 49f0a54f0bdcba297bac194d8dafe431
+url = https://golang.org/dl/go1.16.13.src.tar.gz
+md5sum = 1c076f952d9af57590a36fa7d36f695a
 
 # go1.16 needs go1.4 to bootstrap
 environment-extra =