Another fix for lua_yield() from C hook.

Reported by Jason Carr.

src/lj_ccallback.c

@@ -549,13 +549,13 @@ static void callback_conv_args(CTState *cts, lua_State *L)
   if (LJ_FR2) {
     (o++)->u64 = LJ_CONT_FFI_CALLBACK;
     (o++)->u64 = rid;
-    o++;
   } else {
     o->u32.lo = LJ_CONT_FFI_CALLBACK;
     o->u32.hi = rid;
     o++;
   }
   setframe_gc(o, obj2gco(fn), fntp);
+  if (LJ_FR2) o++;
   setframe_ftsz(o, ((char *)(o+1) - (char *)L->base) + FRAME_CONT);
   L->top = L->base = ++o;
   if (!ct)

src/lj_err.c

@@ -687,9 +687,9 @@ LJ_NOINLINE void lj_err_optype_call(lua_State *L, TValue *o)
   const BCIns *pc = cframe_Lpc(L);
   if (((ptrdiff_t)pc & FRAME_TYPE) != FRAME_LUA) {
     const char *tname = lj_typename(o);
+    setframe_gc(o, obj2gco(L), LJ_TTHREAD);
     if (LJ_FR2) o++;
     setframe_pc(o, pc);
-    setframe_gc(o, obj2gco(L), LJ_TTHREAD);
     L->top = L->base = o+1;
     err_msgv(L, LJ_ERR_BADCALL, tname);
   }

src/lj_frame.h

@@ -46,7 +46,7 @@ enum {
 #define frame_gc(f)		(gcval((f)-1))
 #define frame_ftsz(f)		((ptrdiff_t)(f)->ftsz)
 #define frame_pc(f)		((const BCIns *)frame_ftsz(f))
-#define setframe_gc(f, p, tp)	(setgcVraw((f)-1, (p), (tp)))
+#define setframe_gc(f, p, tp)	(setgcVraw((f), (p), (tp)))
 #define setframe_ftsz(f, sz)	((f)->ftsz = (sz))
 #define setframe_pc(f, pc)	((f)->ftsz = (int64_t)(intptr_t)(pc))
 #else

src/lj_meta.c

@@ -86,8 +86,8 @@ int lj_meta_tailcall(lua_State *L, cTValue *tv)
   else
     top->u32.lo = LJ_CONT_TAILCALL;
   setframe_pc(top++, pc);
-  if (LJ_FR2) top++;
   setframe_gc(top, obj2gco(L), LJ_TTHREAD);  /* Dummy frame object. */
+  if (LJ_FR2) top++;
   setframe_ftsz(top, ((char *)(top+1) - (char *)base) + FRAME_CONT);
   L->base = L->top = top+1;
   /*