Fix #1286, #2099: Add `sphinx.ext.autosectionlabel` extension to allow reference sections using its title

doc/ext/autosectionlabel.rst

@@ -0,0 +1,25 @@
+.. highlight:: rest
+
+:mod:`sphinx.ext.autosectionlabel` -- Allow reference sections using its title
+==============================================================================
+
+.. module:: sphinx.ext.autosectionlabel
+   :synopsis: Allow reference section its title.
+
+.. versionadded:: 1.4
+
+This extension allows you to refer sections its title.  This affects to the
+reference role (:rst:role:`ref`).
+
+For example::
+
+    A Plain Title
+    -------------
+
+    This is the text of the section.
+
+    It refers to the section title, see :ref:`A Plain Title`.
+
+
+Internally, this extension generates the labels for each section.  If same
+section names are used in whole of document, any one is used for a target.