LibGD 2.2.1 release

Hot on the tail of the 2.2.0 release, we've got 2.2.1 ready! A security issue was missed in the previous bug triaging but that's in here now.

This is a recommended update.

You can download the 2.2.1 version of GD Graphics Library from the libgd project.

Check out the full commits list since the previous release.