patch 8.0.0034
Problem:    No completion for ":messages".
Solution:   Complete "clear" argument. (Hirohito Higashi)
diff --git a/src/vim.h b/src/vim.h
index a787575..0ac296e 100644
--- a/src/vim.h
+++ b/src/vim.h
@@ -793,6 +793,7 @@
 #define EXPAND_SYNTIME		43
 #define EXPAND_USER_ADDR_TYPE	44
 #define EXPAND_PACKADD		45
+#define EXPAND_MESSAGES		46
 
 /* Values for exmode_active (0 is no exmode) */
 #define EXMODE_NORMAL		1