adding rlimit resource limit facility to provide platform and architecture independent method for canceling activities

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

src/util/rlimit.h

@@ -0,0 +1,47 @@
+/*++
+Copyright (c) 2015 Microsoft Corporation
+
+Module Name:
+
+    rlimit.h
+
+Abstract:
+
+    Resource limit container.
+
+Author:
+
+    Nikolaj Bjorner (nbjorner) 2015-09-28
+
+Revision History:
+
+--*/
+#ifndef RLIMIT_H_
+#define RLIMIT_H_
+
+#include "vector.h"
+
+class reslimit {
+    unsigned        m_count;
+    unsigned        m_limit;
+    unsigned_vector m_limits;
+public:    
+    reslimit();
+    bool inc();
+    bool inc(unsigned offset);
+    void push(unsigned delta_limit);
+    void pop();
+    unsigned count() const; 
+};
+
+class scoped_rlimit {
+    reslimit& m_limit;
+public:
+    scoped_rlimit(reslimit& r, unsigned l): m_limit(r) {
+        r.push(l);
+    }
+    ~scoped_rlimit() { m_limit.pop(); }
+
+};
+
+#endif