pull in Win32-extras, to be able to get current process id in Windows

Fixed up a number of things that had worked around there not being a way to
get that.

Most notably, transfer info files on windows now include the process id,
since no locking is currently done. This means the file format varies
between windows and unix.

Remote/Rsync.hs

@@ -23,7 +23,7 @@ import qualified Data.Map as M
 #ifndef mingw32_HOST_OS
 import System.Posix.Process (getProcessID)
 #else
-import System.Random (getStdRandom, random)
+import System.Win32.Process.Current (getCurrentProcessId)
 #endif
 
 import Common.Annex
@@ -243,7 +243,7 @@ withRsyncScratchDir a = do
 #ifndef mingw32_HOST_OS
 	v <- liftIO getProcessID
 #else
-	v <- liftIO (getStdRandom random :: IO Int)
+	v <- liftIO getCurrentProcessId
 #endif
 	t <- fromRepo gitAnnexTmpDir
 	createAnnexDirectory t