patch 8.1.0354: packadd test fails on MS-Windows

Problem:    Packadd test fails on MS-Windows.
Solution:   Ignore difference between forward and backward slashes.
diff --git a/src/version.c b/src/version.c
index 840f288..480d20e 100644
--- a/src/version.c
+++ b/src/version.c
@@ -795,6 +795,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    354,
+/**/
     353,
 /**/
     352,