Canonical URL comparison for last page check

[ldodds]

Section 5.1.5 says that the last page is reached if:

• The items property is an empty array.
• The next property matches the URL of the current page.

But we should be clearer on what "matches" mean:

• Some feeds already have relative URLs which means clients must create an absolute URL before doing a comparison
• Should the URLs be canonicalised in some way to ensure that parameters are compared in the right order?

[ldodds]

I now realise that the specification says that the next page link must be absolute. Some implementations aren't doing that. But that's a conformance issue.