This also removes re-definition of description environment which is not
needed anymore as ``\labelsep`` is not modified.

The removal of an `\everyeof{}` from `\sphinxcode` was causing
never-ending loop if the latter expanded inside `\sphinxhref`. The bug
was introduced at 3128a43, it thus never made it to a release yet.
Catching it in time for 1.5.4.

Although the data in ``\pdfinfo`` as set-up in ``sphinxmanual.cls`` was
ignored, some LaTeX commands (e.g. ``\large``) in the ``latex_documents``
title item could cause failed PDF builds.

This commit removes the anyhow ignored ``\pdfinfo`` usage, and indicates
in commented-out lines how to use ``\hypersetup``, which may be done in
master branch, or possibly in stable branch, if some consensus emerges
about how to represent ``\and`` in the ``/Author`` field. It seems the
PDF Document Information Dictionary does not seem to provide any
universal multi-lingual way to indicate multiple authors.

All LaTeX commands such as \textbf, \emph, \underline.. are "short",
thus there was no need of ``\long`` prefix. Regarding
``\sphinxoptional`` which was defined via ``\newcommand``, the ``\long``
is there for full backwards compatibility, but a priori the argument
will always be a "short" one (i.e. not containing empty line or ``\par``
token.)