Add some fmt::show implementations to make debugging layout easier.
Initial spec-incompliant implementation of default click action for anchor elements.

This is cherry-picked from https://github.com/mozilla/servo/pull/1688:

  * Initial spec-incompliant implementation of default click action for anchor elements.
  * Add documentation; gut the new document URL loading method
    and move it all into the new Window method.
  * Add test for default event prevention.

Original developer: Josh Matthews <josh@joshmatthews.net>
Make ComputedStyle fields private and add getters.

This isolates layout code from upcoming refactoring in properties.rs.mako.
Un-disable and fix some warnings in the style crate.
Remove CowArc and use the new Arc::make_unique() method instead.
Add LIBRARY_PATH env var to help the linux build slave.
auto merge of #2479 : metajack/servo/linux-library-path, r=metajack
Remove *() hack now that rust upgrade is complete. Fixes memory corruption bug #2412.
Replace deprecated rev_iter() by iter().rev().
auto merge of #2441 : saneyuki/servo/event, r=jdm

- Fix #2118
- Take over from #2293
Implement CustomEvent (#2173)
auto merge of #2374 : Manishearth/servo/customevent, r=jdm

This was previously PR'd on #2218
auto merge of #2468 : glennw/servo/show-traits, r=jdm
auto merge of #2471 : bjz/servo/split-to-width, r=pcwalton

@pcwalton r?
Remove the workaround for Rust issue 10683.
auto merge of #2472 : mbrubeck/servo/2137-done-deps, r=metajack

Part of the fix for #2137.  This allows submodules to correctly recompile (or not) based on all of the dependency information from `mk/sub.mk`.  Along with this change, we will also need to make changes to each of the affected submodules' make files, for example in `rust-azure/Makefile.in`:

```diff
-libazure.dummy: azure.rc $(RUST_SRC) libazure.a ../../skia/skia/libskia.a
+libazure.dummy: azure.rc $(RUST_SRC) libazure.a $(EXT_DEPS)
```

r? @metajack
auto merge of #2482 : Ms2ger/servo/rev_iter, r=jdm
auto merge of #2483 : zwarich/servo/remove-10683-workaround, r=jdm
Eliminate pointless copies of ImageResponseMsg in the image task.
auto merge of #2485 : zwarich/servo/eliminate-copy, r=jdm