Treat custom environment as verbatim on export

[Jacob Gerlach <jacobgerlach@gmail.com>]

Hello,

I want to use a one of several custom environments for some babel
results using, for example, ":wrap myverbatim" as a header argument.
(Since I have several possible environments, I think I need to use
:wrap rather than, say, replacing "verbatim" using an export filter).

However, since this block isn't recognized as an actual verbatim
environment, markup gets processed in undesirable ways.

For example:

-------------
#+BEGIN_SRC sh :exports results :wrap myverbatim
echo "Hello_world"
#+END_SRC

#+RESULTS:
#+BEGIN_myverbatim
Hello_world
#+END_myverbatim
-------------
exports to
-------------
\begin{myverbatim}
Hello\(_{\text{world}}\)
\end{myverbatim}
-------------
instead of
-------------
\begin{myverbatim}
Hello_world
\end{myverbatim}
-------------

A couple questions:

- Is there any way I've missed to specify verbatim export as an option
for an arbitrary block/environment?

- If not, I think that I need a derived exporter to achieve this, but
the `contents' of a special-block have already had markup transcoded
by the time the derived backend function sees them. What functions
would my derived backend need to replace to allow applying verbatim
formatting to block types of my choosing?

Thanks for any tips,
Jake