Sizzle: assume window.document in Sizzle.matches; massively reduce calls to setDocument by not calling when context is null

Adjust jQuery('html') detection to only match when html starts with '<' (not counting space characters). Fixes #11290.

Fix #4087. insertAfter, insertBefore, etc do not work if origin and destination are same element. Close gh-1068.

Remove clear(merge)Attributes hack

Pass style declarations around for performance improvements and paving the way for the css array signature
Also, simplify the jQuery.css numeric coercion signature

Depends on jquery/sizzle#177, included with the Sizzle submodule in this commit.

This fixes jquery/testswarm#197. These are currently removed from
the TestSwarm injector, however this is jQuery specific, and
should be done from this end instead.

Signed-off-by: Rick Waldron <waldron.rick@gmail.com>