patch 8.0.0554: toupper and tolower don't work properly for Turkish

Problem:    Toupper and tolower don't work properly for Turkish when 'casemap'
            contains "keepascii". (Bjorn Linse)
Solution:   When 'casemap' contains "keepascii" use ASCII toupper/tolower.
diff --git a/src/version.c b/src/version.c
index 9fb32c9..578cfe3 100644
--- a/src/version.c
+++ b/src/version.c
@@ -765,6 +765,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    554,
+/**/
     553,
 /**/
     552,