Quoting from the patch:
We compare against Go's built-in GCM implementation. Since stupidgcm only
supports 128-bit IVs and Go only supports that from 1.5 onward, we cannot
run these tests on older Go versions.
...complete with tests and benchmark.
This will allow us to get rid of the dependency to spacemonkeygo/openssl
that causes problems on Arch Linux
( https://github.com/rfjakob/gocryptfs/issues/21 )