This is done by moving the sorting from the glossary directive to a
transform operating after the i18n transform.

Closes #9827

Document indent behaviour for directives

New Sphinx tutorial, part III

Mention how the indent of the contents for directives is chosen and what
the effect on directives which are sensitive to whitespace is,
e.g. code-block.

The presence or absence of the ``:dedent: 4`` option in the example

.. code-block:: ruby
   :dedent: 4

       some ruby code

makes no difference for the output due to how ReST handles whitespace.
If it is present, then ReST indent is 3 and the 4 spaces of the code are
stripped by the :dedent: option.  If the dedent option is missing, then
the ReST indent is 7 and all whitespace is stripped again.

Add a dummy option to fixate the ReST indent to 3, so adding and
removing of the option in the example has an effect on the output.