Put non-object tmp files in .git/annex/misctmp, leaving .git/annex/tmp for only partially transferred objects.

This allows eg, putting .git/annex/tmp on a ram disk, if the disk IO
of temp object files is too annoying (and if you don't want to keep
partially transferred objects across reboots).

.git/annex/misctmp must be on the same filesystem as the git work tree,
since files are moved to there in a way that will not work cross-device,
as well as symlinked into there.

I first wanted to put the tmp objects in .git/annex/objects/tmp, but
that would pose transition problems on upgrade when partially transferred
objects existed.

git annex info does not currently show the size of .git/annex/misctemp,
since it should stay small. It would also be ok to make something clean it
out, periodically.

Annex/Content.hs

@@ -221,7 +221,7 @@ getViaTmpChecked check key action =
  -}
 prepGetViaTmpChecked :: Key -> Annex Bool -> Annex Bool
 prepGetViaTmpChecked key getkey = do
-	tmp <- fromRepo $ gitAnnexTmpLocation key
+	tmp <- fromRepo $ gitAnnexTmpObjectLocation key
 
 	e <- liftIO $ doesFileExist tmp
 	alreadythere <- if e
@@ -250,7 +250,7 @@ finishGetViaTmp check key action = do
 
 prepTmp :: Key -> Annex FilePath
 prepTmp key = do
-	tmp <- fromRepo $ gitAnnexTmpLocation key
+	tmp <- fromRepo $ gitAnnexTmpObjectLocation key
 	createAnnexDirectory (parentDir tmp)
 	return tmp