Use `Any` for the layout data.

Breaks the dependency between `gfx` and `script`, which is nice.
Fix the crash on #582. Combining characters are still not shown because this is not implemented. With @sonwow
auto merge of #1208 : pcwalton/servo/any-layout-data, r=metajack

Breaks the dependency between `gfx` and `script`, which is nice.

This exposed some performance issues with Rust's `Any` type, which I've filed:

https://github.com/mozilla/rust/issues/10382
Make list-item's display style block
Rename main/layout/aux.rs -> main/layout/extra.rs. (#1226)
Cleanup attribute setting functions a bit.
Make Attr::local_name always initialized.
auto merge of #1247 : saneyuki/servo/rename, r=metajack

@metajack ?
auto merge of #1249 : Ms2ger/servo/set-attr, r=kmcallister
Implement Rule Hash for Selector Matching.

+ Add index fields in Rule for parent StyleRule and parent Stylesheet to break
  ties while cascading.
  Sorting by (specificity, stylesheet index, rule index) removes the need to use stable sorts.
Insert and lookup element selectors case-insensitively.

Both the insertion key for rules having a LocalNameSelector and the lookup-key sent in
get_all_matching_rules should be ASCII lower case.
Append to a vector argument instead of returning an owned vector.

Also, use stack-allocated vector for fixed-length vector instead of allocating
on the heap.
Avoid one allocation in selector matching
auto merge of #1251 : Ms2ger/servo/attr-localname, r=kmcallister
auto merge of #1254 : pcwalton/servo/rule-hash, r=pcwalton

This is @pradeep90's PR with one little optimization.
auto merge of #1231 : sonwow/servo/list-item, r=SimonSapin
Fix compute height using 'height' property
configure: Refuse to do anything if a submodule has a dirty working tree

This isn't a full fix for #522 / #835 but it prevents the unrecoverable
loss of work without changing the behavior of configure generally.

If configure drops committed local work, it can be recovered from the reflog.
Change GitHub http submodules to https.
Stop passing DOMStrings via borrowed pointer. (#1201)