windows: Fix process termination code.

The ctrl-c hack used before didn't actually seem to work.

No haskell libraries expose TerminateProcess. I tried just calling it via
FFI, but got segfaults, probably to do with the wacky process handle not
being managed correctly. Moving it all into one C function worked.

This was hell. The EvilLinker hack was just final icing on the cake.
We all know what the cake was made of.

Utility/WinProcess.hs

@@ -0,0 +1,19 @@
+{- Windows processes
+ -
+ - Copyright 2014 Joey Hess <joey@kitenet.net>
+ -
+ - Licensed under the GNU GPL version 3 or higher.
+ -}
+
+{-# LANGUAGE ForeignFunctionInterface #-}
+
+module Utility.WinProcess where
+
+import Utility.PID
+
+import System.Win32.Process
+import Foreign.C
+import Control.Exception
+
+foreign import ccall unsafe "terminatepid"
+	terminatePID :: PID -> IO ()