patch 8.0.0553: toupper/tolower test fails on Mac

Problem:    Toupper/tolower test with Turkish locale fails on Mac.
Solution:   Skip the test on Mac.
diff --git a/src/version.c b/src/version.c
index e37178b..9fb32c9 100644
--- a/src/version.c
+++ b/src/version.c
@@ -765,6 +765,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    553,
+/**/
     552,
 /**/
     551,