Hi all,

This patch adds a couple "boundary checks" to the verbatim folding code
I contributed earlier.

Here's a sample document illustrating what could go wrong:

--8<---------------cut here---------------start------------->8---
\documentclass{article}
\usepackage{pythontex}
\NewDocumentCommand{\pyvm}{ m }{\mbox{\pyv{#1}}}

\begin{document}

$\pyvm{42}$

\end{document}
--8<---------------cut here---------------end--------------->8---

With the previous code, folding would trigger on \pyvm{42} as if it were
\pyv with delimiter m.  The fix is to require a word boundary in the
macro-matching regexp.

The other change is a bounds check.  I made this change locally a few
months ago, and think it was motivated by a parsing error, but
unfortunately forgot to save a minimal reproduction.

Any feedback welcome.

Thanks, best,

Paul