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- Include unpublished Dt headers in Dt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 for unpublished Motif functions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

@@ -95,7 +95,7 @@ extern unsigned char * _DtWmParseNextChar(
 extern int _DtWmParseLineNumber( 
                         DtWmpParseBuf *pWmPB) ;
 extern void _DtWmParseToLower (
-			unsigned char  *string);
+			char  *string);
 extern unsigned int _DtWmParsePeekAhead(
 			unsigned char *currentChar,
 			unsigned int currentLev) ;