Add a Sphinx extension to copy over Retina images.

Review Request #5511 — Created Feb. 20, 2014 and submitted — Latest diff uploaded

Information

Review Board
release-2.0.x
ccb31ce...

Reviewers

Sphinx only actually copies over images that are used in documents. This
means that while we can dump @2x copies of images into _static, they
won't be used.

This extension hooks into the environment generation and html page
collection events, looking for @2x equivalents for all images that are
in use. It then adds them to the list of images set to be copied into
_images.

Built the docs and saw the Retina images copied over, which successfully
loaded on the page.