dtfile: Add missing prototypes

Add missing prototypes and header files to the dtfile
code in order to move closer towards 64-bit compatibility.

Extract the following functions from Motif internal headers:

_XmGetWidgetExtData
_XmRecordEvent
_XmStringUngenerate
_XmTextFieldSetDestination
_XmGetActiveTopLevelMenu

Extract manually prototypes of the obsolete Motif interface:
_XmHighlightBorder
_XmUnhighlightBorder

Remove XmPrivate.h if extractprototype.awk fails

Make the following header files available via -I:
	codelibs/boolean.h
	codelibs/pathutils.h
	codelibs/shellutils.h
and remove shellutils.h from dtwm directory.

cde/programs/dtfile/Encaps.c

@@ -83,25 +83,21 @@
 #include <Xm/AtomMgr.h>
 #include <Xm/MwmUtil.h>
 #include <Xm/VendorSEP.h>
+#include <Xm/XmPrivate.h> /* _XmStringUngenerate, _XmGetWidgetExtData */
 #include <X11/ShellP.h>
 #include <X11/Shell.h>
 #include <X11/Xutil.h>
 #include <X11/Xatom.h>
 #include <X11/Intrinsic.h>
-/* Copied from Xm/BaseClassI.h */
-extern XmWidgetExtData _XmGetWidgetExtData(
-                        Widget widget,
-#if NeedWidePrototypes
-                        unsigned int extType) ;
-#else
-                        unsigned char extType) ;
-#endif /* NeedWidePrototypes */
 
 #include <Dt/Wsm.h>
 #include <Dt/DtNlUtils.h>
 
 #include "Encaps.h"
+#include "Desktop.h"
 #include "Filter.h"
+#include "FileMgr.h"
+#include "Main.h"
 #include "ModAttr.h"