*) reset cached dirent.d_type after stat()
   this fixes slash after link to a directory in ngx_http_autoindex_module;
*) use cached dirent.d_type as hint on all systems

the issues has been introduced in r2235
diff --git a/src/os/unix/ngx_files.c b/src/os/unix/ngx_files.c
index 2154bed..618d4e2 100644
--- a/src/os/unix/ngx_files.c
+++ b/src/os/unix/ngx_files.c
@@ -274,9 +274,8 @@
     if (dir->de) {
 #if (NGX_HAVE_D_TYPE)
         dir->type = dir->de->d_type;
-        dir->valid_type = dir->type ? 1 : 0;
 #else
-        dir->valid_type = 0;
+        dir->type = 0;
 #endif
         return NGX_OK;
     }