Merge of r4963: proxy: better error message about unexpected data.

Requested by Igor Sysoev.

src/http/modules/ngx_http_proxy_module.c

@@ -1610,7 +1610,8 @@ ngx_http_proxy_copy_filter(ngx_event_pipe_t *p, ngx_buf_t *buf)
         p->upstream_done = 1;
 
         ngx_log_error(NGX_LOG_WARN, r->connection->log, 0,
-                      "upstream sent too much data");
+                      "upstream sent more data than specified in "
+                      "\"Content-Length\" header");
     }
 
     return NGX_OK;