newpv none PV
pv_cur bstate->bs_pv.xpv_cur STRLEN
pv_free bstate->bs_pv none x
-sv_upgrade bstate->bs_sv char x
+sv_upgrade bstate->bs_sv U8 x
sv_refcnt SvREFCNT(bstate->bs_sv) U32
sv_refcnt_add SvREFCNT(bstate->bs_sv) I32 x
sv_flags SvFLAGS(bstate->bs_sv) U32