solver factories, cleanup solver API, simplified strategic solver, added combined solver

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>

src/solver/combined_solver.h

@@ -0,0 +1,32 @@
+/*++
+Copyright (c) 2012 Microsoft Corporation
+
+Module Name:
+
+    combined_solver.cpp
+
+Abstract:
+
+    Implements the solver API by combining two solvers.
+
+    This is a replacement for the strategic_solver class.
+
+Author:
+
+    Leonardo (leonardo) 2012-12-11
+
+Notes:
+
+--*/
+#ifndef _COMBINED_SOLVER_H_
+#define _COMBINED_SOLVER_H_
+
+#include"params.h"
+
+class solver;
+class solver_factory;
+
+solver * mk_combined_solver(solver * s1, solver * s2, params_ref const & p);
+solver_factory * mk_combined_solver_factory(solver_factory * f1, solver_factory * f2);
+
+#endif