fix for
f83b46a0147ba6f476add85d17f61a7e7fb00f21, which added
the new SAVEt_GVSV, but forgot to amend the CX srack duplication code.
(Since that code is only used on win32, I'm applying it blind here)
TOPPTR(nss,ix) = sv_dup_inc(sv, param);
/* fall through */
case SAVEt_ITEM: /* normal string */
+ case SAVEt_GVSV: /* scalar slot in GV */
case SAVEt_SV: /* scalar reference */
sv = (const SV *)POPPTR(ss,ix);
TOPPTR(nss,ix) = sv_dup_inc(sv, param);