Remove suggestion to use #[must_root] for functions
Cleanup the implementation of HTMLTableElement::GetCaption.
More useful stb-image error handling
auto merge of #3862 : Manishearth/servo/lint-fix, r=jdm

The correct thing to do here is to use `#[allow(unrooted_must_root)]` (the warning already mentions this). `#[must_root]` on functions does nothing.
auto merge of #3863 : Ms2ger/servo/cleanup-caption, r=Manishearth
Have ContentBox(es)Queries consult the flow tree

Instead of looking at the display tree, have ContentBox(es)Query consult
the flow tree. This allow optimizing away parts of the display tree
later. To do this we need to be more careful about how we send reflow
requests, only querying the flow tree when possible.

Fixes #3790.
auto merge of #3857 : mrobinson/servo/queries, r=pcwalton

Instead of looking at the display tree, have ContentBox(es)Query consult
the flow tree. This allow optimizing away parts of the display tree
later. To do this we need to be more careful about how we send reflow
requests, only querying the flow tree when possible.

Fixes #3790.
auto merge of #3872 : kmcallister/servo/stb-error, r=jdm
Removes the useless 'static constraint on SmallVec.

It was likely added accidentally after a rustc upgrade.

r? @jdm
auto merge of #3875 : cgaebel/servo/remove-static-constraint-on-smallvec, r=jdm

It was likely added accidentally after a rustc upgrade.

r? @jdm