patch 9.1.0469: Cannot have buffer-local value for 'completeopt'

Problem:  Cannot have buffer-local value for 'completeopt'
          (Nick Jensen).
Solution: Make 'completeopt' global-local (zeertzjq).

Also for some reason test Test_ColonEight_MultiByte seems to be failing
sporadically now. Let's mark it as flaky.

fixes: #5487
closes: #14922

Signed-off-by: zeertzjq <zeertzjq@outlook.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/structs.h b/src/structs.h
index bd6977e..f1bbf17 100644
--- a/src/structs.h
+++ b/src/structs.h
@@ -3222,6 +3222,8 @@
 #ifdef FEAT_FOLDING
     char_u	*b_p_cms;	// 'commentstring'
 #endif
+    char_u	*b_p_cot;	// 'completeopt' local value
+    unsigned	b_cot_flags;	// flags for 'completeopt'
     char_u	*b_p_cpt;	// 'complete'
 #ifdef BACKSLASH_IN_FILENAME
     char_u	*b_p_csl;	// 'completeslash'