Stream: fixed possible integer overflow in rate limiting.

src/stream/ngx_stream_proxy_module.c

diff --git a/src/stream/ngx_stream_proxy_module.c b/src/stream/ngx_stream_proxy_module.c
index 761e5f7..c25d6a1 100644
--- a/src/stream/ngx_stream_proxy_module.c
+++ b/src/stream/ngx_stream_proxy_module.c
@@ -1062,7 +1062,7 @@
                     break;
                 }
 
-                if (size > (size_t) limit) {
+                if ((off_t) size > limit) {
                     size = (size_t) limit;
                 }
             }