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- Include unpublished Dt headers in Dt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 for unpublished Motif functions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/WmWrkspace.h

@@ -100,6 +100,7 @@ extern WsClientData * GetWsClientData(
                         ClientData *pCD) ;
 extern void SetClientWsIndex( 
                         ClientData *pCD) ;
+void ProcessDtWmHints (ClientData *pCD) ;
 extern Boolean ProcessWorkspaceHints( 
                         ClientData *pCD) ;
 extern void ProcessWorkspaceHintList(