old_params ==> front_end_params. Isolated abstract solver interface

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

src/solver/progress_callback.h

@@ -0,0 +1,33 @@
+/*++
+Copyright (c) 2008 Microsoft Corporation
+
+Module Name:
+
+    progress_callback.h
+
+Abstract:
+
+    Virtual callback for reporting progress.
+
+Author:
+
+    Michal Moskal (micmo) 2009-02-17.
+
+Revision History:
+
+--*/
+#ifndef _PROGRESS_CALLBACK_H_
+#define _PROGRESS_CALLBACK_H_
+
+class progress_callback {
+public:
+    virtual ~progress_callback() {}
+    
+    // Called on every check for resource limit exceeded (much more frequent).
+    virtual void fast_progress_sample() {}
+
+    // Less frequent invoked.
+    virtual void slow_progress_sample() {}
+};
+
+#endif