patch 9.0.0756: no autocmd event for changing text in a terminal window

Problem:    No autocmd event for changing text in a terminal window.
Solution:   Add TextChangedT. (Shougo Matsushita, closes #11366)
diff --git a/src/vim.h b/src/vim.h
index 57368f3..5d8c738 100644
--- a/src/vim.h
+++ b/src/vim.h
@@ -1394,6 +1394,7 @@
     EVENT_TEXTCHANGED,		// text was modified not in Insert mode
     EVENT_TEXTCHANGEDI,		// text was modified in Insert mode
     EVENT_TEXTCHANGEDP,		// TextChangedI with popup menu visible
+    EVENT_TEXTCHANGEDT,		// text was modified in Terminal mode
     EVENT_TEXTYANKPOST,		// after some text was yanked
     EVENT_USER,			// user defined autocommand
     EVENT_VIMENTER,		// after starting Vim