Update from git servo/rust-geom to crates.io euclid

[SimonSapin]

rust-geom has been renamed to euclid (because geom was already taken) and published on crates.io. We should update Servo and its dependencies accordingly. In components/servo/Cargo.lock I count 4 crates in other repositories that need to updated:

• azure https://github.com/servo/rust-azure/
• io-surface https://github.com/servo/rust-io-surface/
• layers https://github.com/servo/rust-layers
• offscreen_gl_context https://github.com/ecoal95/rust-offscreen-rendering-context

… and 16 in this repository:

• canvas
• canvas_traits
• compositing
• gfx
• glutin_app
• layout
• layout_traits
• msg
• net
• net_traits
• script
• script_traits
• style
• style_tests
• util
• util_tests

In each case:

• this section of Cargo.toml:

  [dependencies.geom]
  git = "https://github.com/servo/rust-geom"

  needs to be replaced with geom = "0.1" in the [dependencies] section

• extern crate geom; in lib.rs needs to be replaced with extern crate euclid as geom; or extern crate euclid;. In the latter case, the rest of the code also needs to be updated with the new name.

[Hockenberry]

Should this issue should be closed?

[SimonSapin]

Yes, thanks. Fixed in #6423.