[1.1.X] Removed a couple completed TODO items from the documentation documentation.

The work is mostly done, but here's what's left, in rough order of priority.

    * Change the "Added/changed in development version" callouts to proper

      Sphinx ``.. versionadded::`` or ``.. versionchanged::`` directives.

    * Check for and fix malformed links. Do this by running ``make linkcheck``

      and fix all of the 300+ errors/warnings.

      In particular, look at all the relative links; these need to be

      changed to proper references.

    * Most of the various ``index.txt`` documents have *very* short or even

      non-existent intro text. Each of those documents needs a good short intro

      the content below that point.