Auto merge of #309 - tiaanl:new-csscolor, r=emilio

Implement [ok]lab, [ok]lch from color-4 spec.

https://w3c.github.io/csswg-drafts/css-color-4/#lab-colors

The size of the new color structs are 32*4 bits which is much bigger than the original 32bit for the RGBA value.  This might change in the future.

Author: bors-servo

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "cssparser"
-version = "0.29.6"
+version = "0.30.0"
 authors = [ "Simon Sapin <simon.sapin@exyr.org>" ]
 
 description = "Rust implementation of CSS Syntax Level 3"