A previous commit removed some, but missed these. Where a location
directive was using Expires to set a future expiry in conjunction
with Cache-Control public, I have replaced the time with an equal
max-age.
Furthermore, Google's web performance guide says that "public" is
implicit if there is a max-age specified.
See: https://developers.google.com/web/fundamentals/performance/optimizing-content-efficiency/http-caching
Make it more obvious which snippets are location based, and which
are just directives. Need to provide more files like basic.conf to
cover more of the common use cases.
Andy Dawson