Create a PhysicsLoopBack that includes both PhysicsClient and PhysicsServer over shared memory.

Add a test for PhysicsLoopBack.

examples/SharedMemory/PhysicsLoopBackC_API.h

@@ -0,0 +1,19 @@
+#ifndef PHYSICS_LOOPBACK_C_API_H
+#define PHYSICS_LOOPBACK_C_API_H
+
+#include "PhysicsClientC_API.h"
+
+#ifdef __cplusplus
+extern "C" { 
+#endif
+
+
+///think more about naming. The b3ConnectPhysicsLoopback
+b3PhysicsClientHandle b3ConnectPhysicsLoopback(int key);
+
+    
+#ifdef __cplusplus
+}
+#endif
+
+#endif //PHYSICS_LOOPBACK_C_API_H