memory leak (1): unset private parameter

[Jun T <takimoto-j@xxxxxxxxxxxxxxxxx>]

valgrind found two memory leaks for which I don't have any quick fix.

This post is for the 1st problem (another post will follow for the 2nd).

% cat unset-private
() {
	private foo
	unset foo
}
% valgrind --leak-check=full zsh -f unset-private

32 bytes in 1 blocks are definitely lost in loss record 247 of 387
  by 0x1935B9: zalloc (mem.c:966)
  by 0x50B0772: makeprivate (param_private.c:138)
  by 0x165D08: scanmatchtable (hashtable.c:433)
  by 0x165D9E: scanhashtable (hashtable.c:449)
  by 0x50B0D7A: bin_private (param_private.c:248)

param_private.c:138 is
    struct gsu_closure *gsu = zalloc(sizeof(struct gsu_closure));

and this 'gsu' is saved in pm->gsu.s.

'unset foo' calls pps_unsetfn(pm, explicit=1), in param_private.c:

314     if (locallevel <= pm->level)
315         gsu->unsetfn(pm, explicit);		# this sets PM_UNSET
316     if (explicit) {
317         pm->node.flags |= PM_DECLARED;
318         pm->gsu.s = (GsuScalar)c;
319     } else
320         zfree(c, sizeof(struct gsu_closure)); # NOT called

When exiting from the function, endparmscope() (indirectly) calls
unsetpm_pm(pm,, explicit=0), but it does not call
pps_unsetfn(pm, expllicit=0) since PM_UNSET is already set
(params.c:3793), and the gsu_closure is not freed.

Maybe we need to set some info in pm to inform unsetpm_pm(pm)
that gsu need be freed (but there is no flag PM_PRIVATE).