Implement HTMLDListElement binding.
Pull libpng in tree to avoid the configuration issue related to libpng.

Most work done by @pliu6
auto merge of #749 : metajack/servo/pliu6-master, r=metajack,me

Most work done by @pliu6

Supercedes #737
Update for glfw-rs bugfix
auto merge of #750 : kmcallister/servo/glfw, r=metajack
Modify Readme for png module.
Merge pull request #754 from saneyuki/readme

Update Readme for png module.
auto merge of #726 : metajack/servo/dlist, r=jdm

r? @jdm
Keep pace with some Rust changes

This doesn't actually include the Rust version update (to 6791021) because the
feature for which I wanted it (debug info) doesn't work, and there's no point
making everyone rebuild until it does.
auto merge of #755 : kmcallister/servo/zip_copies, r=metajack

This doesn't actually include the Rust version update (to `6791021`) because the feature for which I wanted it (debug info) doesn't work, and there's no point making everyone rebuild until it does.
Handle flow trees with block children of inlines.
Handle splitting inlines with interior blocks correctly.
auto merge of #753 : metajack/servo/inline-block, r=eric93

r? @eric93
Drop 'ref' to work around a Rust bug

The bug is mozilla/rust#8675.

Fixes #752.
auto merge of #756 : kmcallister/servo/frametreeiterator, r=metajack

The bug is mozilla/rust#8675.

Fixes #752.
Correct draw order for frame tree layers
Implement compositor layer occlusion; clean up