Add syntactical min checker

The purpose of this patch is to find out more about the "shape" of
the constraints in our benchmarks. In particular, we would like to
determine whether aggregation and negation, together, appear in
recursive rules.

Signed-off-by: Alex Horn <t-alexh@microsoft.com>

src/muz/base/dl_rule_set.h

@@ -179,7 +179,7 @@ namespace datalog {
         void compute_deps();
         void compute_tc_deps();
         bool stratified_negation();
-
+        bool check_min();
     public:
         rule_set(context & ctx);
         rule_set(const rule_set & rs);