dtcreate: Don't crash when clicking "Find Set..."

dtcreate: Don't crash when clicking "Find Set..."

dtcreate crashed on 64-bit system when clicking
"Find Set.." button.

Crash happens in libXm:

    new_w=0x805db4300, args=0x7fffffffb430, num_args=0x7fffffffb3dc)
    at Form.c:1955

$1 = {att = {{type = 4 '\004', w = 0x805db3700, percent = 0, offset = 0,
      value = 0, tempValue = 0}, {type = 1 '\001', w = 0x0, percent = 0,
      offset = 10, value = 0, tempValue = 0}, {type = 3 '\003',
      w = 0x805db3700, percent = 0, offset = 0, value = 0, tempValue = 0}, {
      type = 3 '\003', w = 0x800000000, percent = 0, offset = 10, value = 0,
      tempValue = 0}}, next_sibling = 0x0, sorted = 0 '\0',
  resizable = 1 '\001', preferred_width = 0, preferred_height = 0}

(...)

    at icon_selection_dialog.c:1768
1767            /* Creation of icon_scrolled_win */
1768            icon_scrolled_win = XtVaCreateManagedWidget( "icon_scrolled_win",
1769                            xmScrolledWindowWidgetClass,
1770                            icon_selection_dialog,
1771                            XmNscrollingPolicy, XmAUTOMATIC,
1772    /*                      XmNnavigationType, XmTAB_GROUP, */
1773                            XmNx, 282,
1774                            XmNy, 84,
1775                            XmNscrollBarDisplayPolicy, XmAS_NEEDED,
1776                            XmNrightOffset, 10,
1777                            XmNrightAttachment, XmATTACH_FORM,
1778                            XmNtopOffset, 0,
1779                            XmNtopWidget, icon_container_label,
1780                            XmNtopAttachment, XmATTACH_WIDGET,
1781                            XmNleftOffset, 0,
1782                            XmNleftWidget, icon_container_label,
1783                            XmNleftAttachment, XmATTACH_OPPOSITE_WIDGET,
1784                            XmNbottomOffset, 10,
1785                            XmNbottomWidget, XmATTACH_NONE,
1786                            XmNbottomAttachment, XmATTACH_WIDGET,
1787                            NULL );

What happens here is that ConstraintInitialize receives
four constraints, the last one is this:

    { type = 3 '\003', /* XmATTACH_WIDGET */
      w = 0x800000000, /* malformed XmATTACH_NONE ???
      percent = 0,
      offset = 10, /* specified as XmNbottomOffset */
      value = 0,
      tempValue = 0}

XmATTACH_* values are defined in <Xm/Xm.h> as follows:

   505  enum{   XmATTACH_NONE,                  XmATTACH_FORM,
   506          XmATTACH_OPPOSITE_FORM,         XmATTACH_WIDGET,
   507          XmATTACH_OPPOSITE_WIDGET,       XmATTACH_POSITION,
   508          XmATTACH_SELF
   509          } ;

What is not clear to why XmATTACH_NONE - which should be (int)0 -
becomes 0x800000000 - looks like a 64 bit bug somewhere.

Providing a long value on None (0L) as in this change fixes the
problem.

I understand is that it possible to use such an "empty" widget
is to create additional space at the bottom of the newly created
"icon_scrolled_win".

What needs to be clarified - shouldn't be such an (int) value be
automatically promoted to (long) (or XtArgVal, XtPointer, ...)
and preserve the value 0? Lots of parameters seem to be
passed as ints (for example dimensions) and they do not
appear to cause any trouble.