significant update to Horn routines: add module hnf to extract Horn normal form (removed from rule_manager). Associate proof objects with rules to track (all) rewrites, so that proof traces can be tracked back to original rules after transformations

Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>

src/muz_qe/dl_cmds.cpp

@@ -262,8 +262,10 @@ public:
                 
             case datalog::OK: 
                 break;
+
             default:
-                UNREACHABLE();
+                // exception was raised.
+                break;
             }
             break;
         }