Add option to use handles to RID

Adds an option to compile an alternative implementation for RIDs, which allows checks for erroneous usage patterns as well as providing leak tests.

core/rid.cpp

@@ -30,6 +30,7 @@
 
 #include "rid.h"
 
+#ifndef RID_HANDLES_ENABLED
 RID_Data::~RID_Data() {
 }
 
@@ -38,3 +39,4 @@ SafeRefCount RID_OwnerBase::refcount;
 void RID_OwnerBase::init_rid() {
 	refcount.init();
 }
+#endif // not RID_HANDLES_ENABLED