[css-2017] Fix the indices

[frivoal]

Update / create the index section of the 2017 snapshot

https://drafts.csswg.org/css-2017/#indices

@tabatkins Please either do this, or show me how to.

[frivoal]

@tabatkins I've tried to add the indices to the snapshot (frivoal@7bdf583) based on guessing what the syntax is supposed to be from skimming the source, but it seems I got it wrong.

<index type="dfn" status="TR" spec="
	css21,
	css-syntax-3,
	css-style-attr-1,
	mediaqueries-3,
	css-conditional-3,
        ....
"></index>

This does generate an index of the right kind, but neither the status not the spec filter seem to apply, and I get everyting bikeshed knows about. What's wrong?

[tabatkins]

Ooof, an early shorthand-attribute replacement was turning the spec attribute into data-link-spec, so the index generator was concluding you didn't specify a spec to limit the index to. Fixed now.