Fix warnings in dtwm

- Improve pointer/int compatibility
- Include unpublished Dt headers in Dt
- Use <Xm/XmPrivate.h> for unpublished Motif functions

There are still warnings left generated because
ElementValue.parsed_value should really be a union.

There are also some warnings left because of XtPointer
casting and some unused variables and functions.

cde/programs/dtwm/WmIPC.h

@@ -45,6 +45,13 @@ extern void dtSendWorkspaceModifyNotification(
 	WmScreenData 		*pSD, 
 	Atom 			aWs, 
 	int 			iType);
+extern void dtSendMarqueeSelectionNotification(
+	WmScreenData *pSD,
+	int	type,
+	Position x,
+	Position y,
+	Dimension width,
+	Dimension height);
 
 /********    End Public Function Declarations    ********/