Use Gecko's simpler Bloom filter instead of one based on hash

stretching.

This preserves the usage of the Bloom filter throughout style recalc,
but the implementation is rewritten. Provides a 15% improvement on
Guardians of the Galaxy.

components/util/namespace.rs

@@ -11,3 +11,4 @@ pub fn from_domstring(url: Option<DOMString>) -> Namespace {
         Some(ref s) => Namespace(Atom::from_slice(s.as_slice())),
     }
 }
+