treat .unparsed as plain text

[2bndy5]

This fixes #805.

According to the doxygen manual, users can specify a file extension called .unparsed to disable syntax highlighting. Since this isn't a real language that pygments supports, there was a warning generated when users followed the doxygen manual.

This is a simple patch that replaces the "unparsed" file extension with "text" to invoke pygments' null highlighting lexer.

I also added a code block (that uses \code{.unparsed}) to the doc's example snippets in the codeblocks.rst (and examples/specific/code_blocks.h) to verify this warning is properly suppressed.

[gmarull]

Thanks for the quick response, LGTM

[2bndy5]

I regret that field testing has been the most reliable way to find bugs/shortcomings about v4.33.0. I'll be working on a new PR that will allow the breathe docs to use -W. It seems that they've been ignoring several hundred warnings in the docs' build logs for a while.

[michaeljones]

Good catch and addition.

I've added an explanatory comment which I hope is reasonable. Otherwise I'm happy to merge when you are.

[2bndy5]

Thanks for the additional comment in breathe's src. I'm ok to merge if there are no objections.

[michaeljones]

Ace, thanks for handling it!