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.