patch 8.0.0257: test file missing in distribution

Problem:    The keyword test file is not included in the archive.
Solution:   Update the list of files.
diff --git a/src/version.c b/src/version.c
index 58c9d29..d3dc088 100644
--- a/src/version.c
+++ b/src/version.c
@@ -765,6 +765,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    257,
+/**/
     256,
 /**/
     255,