start porting grobner basis functionality

Signed-off-by: Lev Nachmanson <levnach@hotmail.com>

src/math/lp/nla_grobner.h

@@ -0,0 +1,38 @@
+/*++
+  Copyright (c) 2017 Microsoft Corporation
+
+  Module Name:
+
+  <name>
+
+  Abstract:
+
+  <abstract>
+
+  Author:
+  Nikolaj Bjorner (nbjorner)
+  Lev Nachmanson (levnach)
+
+  Revision History:
+
+
+  --*/
+#pragma once
+
+#include "math/lp/nla_common.h"
+#include "math/lp/nex.h"
+namespace nla {
+class core;
+
+class nla_grobner : common {
+    lp::int_set m_rows;
+    lp::int_set m_active_vars;
+public:
+    nla_grobner(core *core);
+    void grobner_lemmas();
+private:
+    void find_rows();
+    void prepare_rows_and_active_vars();
+    void add_var_and_its_factors_to_q_and_collect_new_rows(lpvar j,  std::queue<lpvar>& q);
+}; // end of grobner
+}