[TASK] Make PHP highlighting work for snippets
This adds the "official" hack to turn on startinline for all php
codeblocks whether they're a snippet or a full file.
Sphinx and docutils don't support setting the startinline option for
pygments. That means that snippets of PHP code that don't have
"<?php ?>" don't get highlighted. The hack was documented here:
Releases: master, 3.0, 2.3, 2.2, 2.1, 2.0, 1.1