delete an element of a ptype_list
ptype_list *delptype(pthead, type)
Pointer to a ptype list
The pointer of this type is to be deleted.
delptype deletes the element of the ptype_list that has the type
type in the list pointed to by pthead.
The list consistency is maintained, and the element put back in the list
of free blocks.
delptype returns a pointer to the new head of list if a typed
pointer used to belong to the list. In most case, it has the value of
pthead. If the type doesn't belong to the list, NULL is
"*** mbk error *** delptype impossible : pthead = NULL"
The pointer to the head of list is NULL, and that clear that
such a list can't be ran thru.
for (i = ptfig->PHINS; i; i = i->NEXT)
i->USER = delptype(i->USER, PLACEABOX);