enable parallel proofs (cf. e8552cba702d), only affects packages so far;
disable quick_and_dirty to make packages produce proofs -- NB: 'sorry' works via "int" mode of proof commands;

--- a/src/Pure/System/isabelle_process.ML	Sat Apr 07 19:28:44 2012 +0200
+++ b/src/Pure/System/isabelle_process.ML	Sat Apr 07 19:59:09 2012 +0200
@@ -167,8 +167,8 @@
     val _ = OS.Process.sleep (seconds 0.5);  (*yield to raw ML toplevel*)
     val _ = Output.physical_stderr Symbol.STX;
 
-    val _ = quick_and_dirty := true;
-    val _ = Goal.parallel_proofs := 0;
+    val _ = quick_and_dirty := false;
+    val _ = Goal.parallel_proofs := 1;
     val _ =
       if Multithreading.max_threads_value () < 2
       then Multithreading.max_threads := 2 else ();