Silence some C++ warnings with PERL_POISON

sv.c throws a few C++ cast warnings when building with PERL_PISN. I'm
not sure that patch is really useful since the testsuite currently fails
when poisoning is enabled, but here it is anyway.
Vincent.

sv.c 2008-06-28 23:11:23.000000000 +0200
sv.c 2008-07-03 11:28:34.000000000 +0200
@@ -181,6 +181,7 @@

#ifdef PERL_PISN
# define SvARENA_CHAIN(sv) ((sv)->sv_u.svu_rv)
+# define SvARENA_CHAIN_set(sv,p) (SvARENA_CHAIN(sv) = (SV *) (p))
/* Whilst I'd love to do this, it seems that things like to check on
unreferenced scalars
# define PSIN_SV_HEAD(sv) PoisonNew(sv, 1, struct STRUCT_SV)
@@ -189,6 +190,7 @@
PoisonNew(&SvREFCNT(sv), 1, U32)
#else
# define SvARENA_CHAIN(sv) SvANY(sv)
+# define SvARENA_CHAIN_set(sv,p) (SvARENA_CHAIN(sv) = (void *) (p))
# define PSIN_SV_HEAD(sv)
#endif

@@ -196,7 +198,7 @@
STMT_START { \
FREE_SV_DEBUG_FILE(p); \
PSIN_SV_HEAD(p); \
- SvARENA_CHAIN(p) = (void *)PL_sv_root; \
+ SvARENA_CHAIN_set(p, PL_sv_root); \
SvFLAGS(p) = SVTYPEMASK; \
PL_sv_root = (p); \
; \
@@ -357,7 +359,7 @@
svend = &sva[SvREFCNT(sva) - 1];
sv = sva + 1;
while (sv < svend) {
- SvARENA_CHAIN(sv) = (void *)(SV*)(sv + 1);
+ SvARENA_CHAIN_set(sv, sv + 1);
#ifdef DEBUGGING
SvREFCNT(sv) = 0;
#endif
@@ -366,7 +368,7 @@
SvFLAGS(sv) = SVTYPEMASK;
sv++;
}
- SvARENA_CHAIN(sv) = 0;
+ SvARENA_CHAIN_set(sv, 0);
#ifdef DEBUGGING
SvREFCNT(sv) = 0;
#endif