Add another exception to error parsing.

* tex-buf.el (TeX-parse-error): Add another exception.
Fix fontification of optional argument to verbatim environments.

* font-latex.el (font-latex-set-syntactic-keywords): Fix
fontification of the optional argument to a verbatim-like
environment.
Fix typo in listings.el.

* style/listings.el ("listings"): Fix typo.

Signed-off-by: Tassilo Horn <tsdh@gnu.org>