Use #if not def _WIN32

Author: satk0

libbf.c

@@ -1711,9 +1711,11 @@ static int __bf_div(bf_t *r, const bf_t *a, const bf_t *b, limb_t prec,
 
         na = n + nb;
 
-        if (sizeof(limb_t) > sizeof(uint64_t) && na >= (SIZE_MAX / sizeof(limb_t)) - 1) {
+#if !defined(_WIN32)
+        if (na >= (SIZE_MAX / sizeof(limb_t)) - 1) {
             return BF_ST_MEM_ERROR;  /* Return memory error status */
         }
+#endif
 
         taba = bf_malloc(s, (na + 1) * sizeof(limb_t));
         if (!taba)