relicense Utility/GPG.hs BSD as the rest of Utility is

The COPYRIGHT had Utility/DirWatcher* listed as GPL, but they were
actually BSD licensed.

No idea why I put the GPL on Utility/GPG.hs file originally.
I wrote all of it, except for guilhem's small changes to it in
00fc21bfec, which seem too small to be
independently copyrightable. I'm relicencing it BSD.

Utility/Gpg.hs

@@ -2,7 +2,7 @@
  -
  - Copyright 2011 Joey Hess <id@joeyh.name>
  -
- - Licensed under the GNU GPL version 3 or higher.
+ - License: BSD-2-clause
  -}
 
 {-# LANGUAGE CPP #-}