BShape: Fix issues for debug build.

As part of the refactoring that was done for app_server layer support,
the private shape_data struct was updated to derive from BReferenceable.
However, BShape's destructor was never updated to reflect this, and
consequently attempts to use a debug build of libbe would consistently
throw the user into the debugger due to BReferenceable's sanity check
against non-zero deletes that weren't on the stack.

It should be noted though that there are probably a few things that could
be factored out and/or simplified with that class in general, since e.g.
when copying its data from another shape_data instance, it uses C++ array
allocations, while when being manipulated by BShape directly, the latter
uses alloc/realloc/free.

src/kits/interface/Shape.cpp

@@ -183,11 +183,12 @@ BShape::BShape(BMessage* archive)
 BShape::~BShape()
 {
 	shape_data* data = (shape_data*)fPrivateData;
+	if (!data->fOwnsMemory) {
+		free(data->opList);
+		free(data->ptList);
+	}
 
-	free(data->opList);
-	free(data->ptList);
-
-	delete (shape_data*)fPrivateData;
+	data->ReleaseReference();
 }