FFI: Drop finalizer table rehash after GC cycle.

Reported by Sergey Kaplun. #1247

src/lj_obj.h

@@ -595,7 +595,7 @@ typedef struct GCState {
   GCSize threshold;	/* Memory threshold. */
   uint8_t currentwhite;	/* Current white color. */
   uint8_t state;	/* GC state. */
-  uint8_t nocdatafin;	/* No cdata finalizer called. */
+  uint8_t unused0;
 #if LJ_64
   uint8_t lightudnum;	/* Number of lightuserdata segments - 1. */
 #else