patch 9.1.0709: GUIEnter event not found in Turkish locale

Problem:   GUIEnter not found in Turkish locale
           (James McCoy, after v9.1.0256, the issue was there before,
            but v9.1.0256 made it more apparent)
Solution:  explicitly compare autocommand events by ASCII value and
           ignoring locale, because according to the documentation,
           events are case insensitive (:h autocommand-events)

fixes: #15574
closes: #15603

Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/proto/strings.pro b/src/proto/strings.pro
index aa8b374..b792edc 100644
--- a/src/proto/strings.pro
+++ b/src/proto/strings.pro
@@ -15,6 +15,7 @@
 size_t vim_strlen_maxlen(char *s, size_t maxlen);
 int vim_stricmp(char *s1, char *s2);
 int vim_strnicmp(char *s1, char *s2, size_t len);
+int vim_strnicmp_asc(char *s1, char *s2, size_t len);
 char_u *vim_strchr(char_u *string, int c);
 char_u *vim_strbyte(char_u *string, int c);
 char_u *vim_strrchr(char_u *string, int c);