Sizzle: account for external document contexts (such as iframes) in combinator checks. Fixes #12572.

I can't think of an uncontrived way to unit test this, it only occurs in IE when a BHO monkeys with the links.

This lets us still add the other offset components to the number so they're less wrong. Affects BlackBerry 5 and iOS 3, everyone else has gBCR.

Chrome fails in ajax.js tests because TestSwarm/Ngnix won't give HEAD requests any respect. Skip them rather than hear Swarmy call FAILURE on each run.

Thanks @vlakoff!

Retains the rooted-at-delegateTarget behavior fixed in #12383 by afd717df.

Thanks @staabm!

See http://editorconfig.org

Update Sizzle: adds custom performance suite for testing across multiple selector engines and multiple versions of Sizzle

http://jqbug.com/12303