better temp name creation for Nitrox -- still very hackish though, but should get us through CASC-23 and CASC-J6

--- a/src/HOL/Tools/Nitpick/lib/Tools/nitrox	Wed Jul 13 22:16:19 2011 +0200
+++ b/src/HOL/Tools/Nitpick/lib/Tools/nitrox	Wed Jul 13 22:16:19 2011 +0200
@@ -18,9 +18,11 @@
 
 [ "$#" -eq 0 -o "$1" = "-?" ] && usage
 
+SCRATCH="Scratch_${PRG}_$$_${RANDOM}"
+
 for FILE in "$@"
 do
-  echo "theory Scratch imports \"Nitpick\" begin ML {* Nitrox.pick_nits_in_fof_file \"$FILE\" *} end;" \
-    > /tmp/$ISABELLE_TMP/Scratch.thy
-  $ISABELLE_PROCESS -e "use_thy \"/tmp/$ISABELLE_TMP/Scratch\"; exit 1;"
+  echo "theory $SCRATCH imports \"Nitpick\" begin ML {* Nitrox.pick_nits_in_fof_file \"$FILE\" *} end;" \
+    > /tmp/$SCRATCH.thy
+  $ISABELLE_PROCESS -e "use_thy \"/tmp/$SCRATCH\"; exit 1;"
 done