patch 9.0.0538: manually deleting test temp files

Problem:    Manually deleting test temp files.
Solution:   Add the 'D' flag to writefile().
diff --git a/src/version.c b/src/version.c
index e6045d7..0bbeae6 100644
--- a/src/version.c
+++ b/src/version.c
@@ -700,6 +700,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    538,
+/**/
     537,
 /**/
     536,