Add some additional BReferenceable debugging.

- When libbe is built in debug mode, BReferenceable now issues a
  debugger call if it's destroyed without all references having been
  released.

src/kits/support/Referenceable.cpp

@@ -6,6 +6,7 @@
 
 #include <Referenceable.h>
 
+#include <debugger.h>
 
 //#define TRACE_REFERENCEABLE
 #ifdef TRACE_REFERENCEABLE
@@ -25,6 +26,10 @@ BReferenceable::BReferenceable()
 
 BReferenceable::~BReferenceable()
 {
+#ifdef DEBUG
+	if (fReferenceCount > 1)
+		debugger("Deleted object which still had references.\n");
+#endif
 }