use off_t in $r->sendfile(), this allows to use 64-bit off_t on platforms

where IV is long:
*) on 64-bit platforms,
*) and on 32-bit platforms if perl was built with -Duse64bitint

src/http/modules/perl/nginx.xs

@@ -607,7 +607,7 @@ sendfile(r, filename, offset = -1, bytes = 0)
 
     ngx_http_request_t        *r;
     char                      *filename;
-    int                        offset;
+    off_t                      offset;
     size_t                     bytes;
     ngx_str_t                  path;
     ngx_buf_t                 *b;