patch 8.0.1596: no autocommand specifically for opening a terminal window

Problem:    No autocommand specifically for opening a terminal window.
Solution:   Add TerminalOpen. (?, closes #2484)
diff --git a/runtime/doc/autocmd.txt b/runtime/doc/autocmd.txt
index e08a7cb..678fb37 100644
--- a/runtime/doc/autocmd.txt
+++ b/runtime/doc/autocmd.txt
@@ -257,6 +257,7 @@
 |BufCreate|		just after adding a buffer to the buffer list
 |BufDelete|		before deleting a buffer from the buffer list
 |BufWipeout|		before completely deleting a buffer
+|TerminalOpen|		after a terminal buffer was created
 
 |BufFilePre|		before changing the name of the current buffer
 |BufFilePost|		after changing the name of the current buffer
@@ -328,6 +329,10 @@
 |CmdlineEnter|		after the cursor moves to the command line
 |CmdlineLeave|		before the cursor leaves the command line
 
+|CmdlineChanged|	after a change was made to the command-line text
+|CmdlineEnter|		after the cursor moves to the command line
+|CmdlineLeave|		before the cursor leaves the command line
+
 |InsertEnter|		starting Insert mode
 |InsertChange|		when typing <Insert> while in Insert or Replace mode
 |InsertLeave|		when leaving Insert mode
@@ -968,6 +973,11 @@
 				for re-loading the syntax file to update the
 				colors, fonts and other terminal-dependent
 				settings.  Executed for all loaded buffers.
+							*TerminalOpen*
+TerminalOpen			Just after a terminal buffer was created, with
+				`:terminal` or |term_start()|. This event is
+				triggered even if the buffer is created
+				without a window, with the ++hidden option.
 							*TermResponse*
 TermResponse			After the response to |t_RV| is received from
 				the terminal.  The value of |v:termresponse|