auto merge of #1137 : SimonSapin/servo/fix-stylesheet-iterator, r=metajack
auto merge of #1140 : SimonSapin/servo/unused-imports, r=metajack
Optimize reflow by changing enums to traits and inlining more
auto merge of #1132 : pcwalton/servo/optimize-reflow, r=larsbergstrom

r? @metajack
submodules: Update submodules.
submodule: Update rust-http to a fixed version
Add rainbow perf test case
Move special cases of CSS 'display' the property to computed value, per spec.
Use Au::scale_by instead of duplicating it.
Fix selector parsing.
Move CSS21 pseudo-elements parsing out of parse_simple_pseudo_class
Implementation of pseudo class 'first-child'.