Fix leak in optimize processing

This applies a patch from OpenSUSE. Source:
https://build.opensuse.org/package/view_file/shells/ksh/ksh93-optimizeleak.dif

| Tue Jul  5 14:49:03 CEST 2016 - mls@suse.de
|
| - fix leak in optimize processing [bnc#982423]
|   new patch: ksh93-optimizeleak.dif

Unfortunately the bug report is not currently public:
https://bugzilla.opensuse.org/show_bug.cgi?id=982423
but this one seems sensible enough and is in production use,
so I'll take it on faith.

src/cmd/ksh93/sh/name.c

@@ -2646,6 +2646,13 @@ void nv_optimize(Namval_t *np)
 		}
 		if((xp= (struct optimize*)fp) && xp->ptr==shp->argaddr)
 			return;
+		if(xp && xp->next)
+		{
+			register struct optimize *xpn;
+			for(xpn = xp->next; xpn; xpn = xpn->next)
+				if(xpn->ptr == shp->argaddr && xpn->np == np)
+					return;
+		}
 		if(op = opt_free)
 			opt_free = op->next;
 		else