patch 9.0.0613: running source tests leaves file behind

Problem:    Running source tests leaves file behind.
Solution:   Add the "D" flag to writefile(). (Dominique Pellé, closes #11243)
            Also do this for other writefile() calls and drop delete().
diff --git a/src/version.c b/src/version.c
index e92207e..1621c81 100644
--- a/src/version.c
+++ b/src/version.c
@@ -700,6 +700,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    613,
+/**/
     612,
 /**/
     611,