patch 8.0.1445: cannot act on edits in the command line

Problem:    Cannot act on edits in the command line.
Solution:   Add the CmdlineChanged autocommand event. (xtal8, closes #2603,
            closes #2524)
diff --git a/src/vim.h b/src/vim.h
index 4765b78..1f9671a 100644
--- a/src/vim.h
+++ b/src/vim.h
@@ -1269,6 +1269,7 @@
     EVENT_BUFWRITEPOST,		/* after writing a buffer */
     EVENT_BUFWRITEPRE,		/* before writing a buffer */
     EVENT_BUFWRITECMD,		/* write buffer using command */
+    EVENT_CMDLINECHANGED,	/* command line was modified*/
     EVENT_CMDLINEENTER,		/* after entering the command line */
     EVENT_CMDLINELEAVE,		/* before leaving the command line */
     EVENT_CMDWINENTER,		/* after entering the cmdline window */