library: eliminate extra stack header space provisions

With the new perspective on potential uses of a 'noop'
enumerator (or whatever we decide to call it) there is
no longer a need to provide for any extra 'user' space
in the stack header structures used by slab & meminfo.

Signed-off-by: Jim Warner <james.warner@comcast.net>

proc/slab.h

@@ -119,7 +119,6 @@ struct slabnode_stack *procps_slabnode_stack_alloc (
 struct slabnode_stack **procps_slabnode_stacks_alloc (
     struct procps_slabinfo *info,
     int maxstacks,
-    int stack_extra,
     int maxitems,
     enum slabnode_item *items);