Update skia dependency.
Merge pull request #327 from metajack/update-skia

Update skia dependency.
Update submodules
Add license check as part of `make tidy` and `make check`
Update skia dependency.
Merge pull request #329 from metajack/update-skia-2

Update skia dependency.
Nuke src/cairo, src/pixman, and src/rust-cairo
Nuke Cairo
Update submodules
gfx: Refactor the Mac platform goop into platform/
Refactor the Linux font stuff
Add license headers
Merge pull request #335 from brson/license

Add license headers
Merge pull request #334 from pcwalton/nuke-cairo

Nuke cairo
Remove native.rs. It's no longer needed; just use platform::* directly.
Remove some module aliases.

These aliases were there for old versions of resolve, and are no longer needed.
Refactor glyph.rs to modern Rust coding style
Refactor the HarfBuzz shaper to be in line with modern Rust style
Rename one of the two modules called "shaper"
Hoist all `extern mod` directives to the top level

This improves compile time and makes `use` directives look cleaner.