enable auto-solve by default

--- a/src/Pure/ProofGeneral/ROOT.ML	Mon Feb 16 10:15:43 2009 +0100
+++ b/src/Pure/ProofGeneral/ROOT.ML	Mon Feb 16 20:45:15 2009 +1100
@@ -18,7 +18,7 @@
   |> setmp Proofterm.proofs 1
   |> setmp quick_and_dirty true
   |> setmp auto_quickcheck true
-  |> setmp auto_solve false) "preferences.ML";
+  |> setmp auto_solve true) "preferences.ML";
 
 use "pgip_parser.ML";