inline pseudo element
Clear tiles before dropping CompositorLayer

This fixes a pixmap leak and task failure (#2069).
Rename before_remove_attr and after_set_attr to allow reusing those names in the next commit.
Add support for trait-based virtual methods on Nodes, and use it for before_remove_attr and after_set_attr.
Integrate Element's after_set/remove behaviour into the virtual method hierarchy.
Add overridable tree binding/unbinding behaviour.
Remove the IElement trait.
Use clear_all_tiles when deleting a sublayer
Make GetCallableProperty more rustic.
auto merge of #2080 : mbrubeck/servo/2069-forget-tiles, r=larsbergstrom

This fixes a pixmap leak and task failure (#2069).
auto merge of #2091 : Ms2ger/servo/GetCallableProperty, r=jdm
Android fixes for February Rust Upgrade
fix android for rust update
Update the configuration files to properly build rust. Revert rust-stb-image submodule misupdate.
auto merge of #2070 : larsbergstrom/servo/android_201404c, r=larsbergstrom,metajack

r? @metajack
auto merge of #2093 : Ms2ger/servo/DOMObjectPointerType, r=jdm
Make register_named_element more efficient
Add a reftest for the pseudo element
Replace @s with Rc types.(fixes #2079)
auto merge of #2085 : lpy/servo/issue2079, r=jdm

see #2079