Reftests

There is a fair amount of reftests in presto-testo, but:
- There are mistakes in the reftest.list files defining the references
- reftest.list files are out of fashion, and link tags in the test files are now preferred (see http://wiki.csswg.org/test/reftest#the-reftest-manifest)

This branch addresses both issues, by fixing the mistakes and converting to link tags.