explict export lists

Eliminated some dead code. In other cases, exported a currently unused
function, since it was a logical part of the API.

Of course this improves the API documentation. It may also sometimes
let ghc optimize code better, since it can know a function is internal
to a module.

364 modules still to go, according to
git grep -E 'module [A-Za-z.]+ where'

Utility/LockFile/LockStatus.hs

@@ -5,7 +5,7 @@
  - License: BSD-2-clause
  -}
 
-module Utility.LockFile.LockStatus where
+module Utility.LockFile.LockStatus (LockStatus(..)) where
 
 import System.Posix