CoreTiming: Ported the CoreTiming namespace from PPSSPP

Implemented the required calls to make it work.

CoreTiming: Added a new logging class Core_Timing.

src/core/arm/arm_interface.h

@@ -103,6 +103,8 @@ public:
         return num_instructions;
     }
 
+    s64 down_count; ///< A decreasing counter of remaining cycles before the next event, decreased by the cpu run loop
+
 protected:
 
     /**