patch 8.1.0779: argument for message functions is inconsistent

Problem:    Argument for message functions is inconsistent.
Solution:   Make first argument to msg() "char *".
diff --git a/src/gui_w32.c b/src/gui_w32.c
index ab60fb5..ceaa041 100644
--- a/src/gui_w32.c
+++ b/src/gui_w32.c
@@ -5128,7 +5128,7 @@
 		    && GetMenuState(s_menuBar, pMenu->id, MF_BYCOMMAND) != -1)
 	    {
 		++msg_hist_off;
-		msg(pMenu->strings[MENU_INDEX_TIP]);
+		msg((char *)pMenu->strings[MENU_INDEX_TIP]);
 		--msg_hist_off;
 		setcursor();
 		out_flush();