auto merge of #533 : pcwalton/servo/slow-debug-code, r=metajack

r? @metajack
Show the error massage if 'o' option is passed.
It's actually uname -m lying.
auto merge of #537 : GlitchMr/servo/darwin-uname-m, r=metajack

I know that this is very small commit, but I guess it still counts, as comment simply lies.
auto merge of #535 : saneyuki/servo/o-opt, r=metajack

I think that we should show the error message until we restore the feature outputting the rendering result to a file.
Add helper functions for floats
Added floats to the flow tree
Allow floats to have specified heights
Fix up problems with float placement
Stop crashing when building the flow tree
auto merge of #542 : eric93/servo/floats, r=pcwalton

I added the minimal amount of code needed to place left-floats on the screen (right floats should also be possible soon). Text does not wrap around floats yet.

One thing I'm curious about is whether some existing abstractions (like Cell) can be used instead of this weird overwriting thing done in float_context.rs.
Update for language changes
auto merge of #546 : brson/servo/master, r=metajack
Updgrade rust-alert
auto merge of #547 : brson/servo/alert, r=metajack

Depends on https://github.com/mozilla-servo/rust-alert/pull/2
Create text runs during box building
auto merge of #539 : sfowler/servo/create-textruns-in-box-builder, r=pcwalton

This is a preliminary step to adding parallel text shaping. In order to have enough time to do a useful amount of work in parallel, we need to trigger text shaping earlier. This PR moves TextRun creation into the box building phase of layout.

I'm pushing this in before the rest of the text shaping patches to avoid bitrot; it's already been through one unpleasant rebase.
Add HashCache and switch all caches from Copy to Clone
Add utility methods to Range
Cache shaped text at word granularity