better directory handling

Rename Locations functions for better consitency, and make their values
more consistent too.

Used </> rather than manually building paths. There are still more places
that manually do so, but are tricky, due to the behavior of </> when
the second FilePath is absolute. So I only changed places where
it obviously was relative.

CmdLine.hs

@@ -111,7 +111,7 @@ shutdown errnum = do
 	-- are left behind to allow resuming on re-run.
 	when (errnum == 0) $ do
 		g <- Annex.gitRepo
-		let tmp = annexTmpLocation g
+		let tmp = gitAnnexTmpDir g
 		exists <- liftIO $ doesDirectoryExist tmp
 		when exists $ liftIO $ removeDirectoryRecursive tmp
 		liftIO $ createDirectoryIfMissing True tmp