patch 8.1.0604: autocommand test fails on MS-Windows

Problem:    Autocommand test fails on MS-Windows.
Solution:   Use pathcmp() instead of strcmp() to check if a directory differs.
diff --git a/src/version.c b/src/version.c
index c73a3ed..10361cb 100644
--- a/src/version.c
+++ b/src/version.c
@@ -800,6 +800,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    604,
+/**/
     603,
 /**/
     602,