more ambitious options (again);

--- a/src/Pure/Tools/dump.scala	Sun Sep 15 13:52:30 2019 +0200
+++ b/src/Pure/Tools/dump.scala	Sun Sep 15 14:01:38 2019 +0200
@@ -212,7 +212,7 @@
         val use_theories_result =
           session.use_theories(used_theories.map(_.theory),
             unicode_symbols = unicode_symbols,
-            share_common_data = false /* FIXME true */,
+            share_common_data = true,
             progress = progress,
             checkpoints = deps.dump_checkpoints,
             commit = Some(Consumer.apply _))