Use servo-freetype instead of the system-native freetype

[fschutt]

See servo/webrender#2617

It seems that freetype-sys, which is what pathfinder uses, links to the system-native freetype version, i.e. whatever you happen to have installed right now. webrender, on the other hand, uses freetype, which is the servo-freetype version, which embeds a full copy of freetype into the binary. This also means that pathfinder shouldn't build on linux if you don't have freetype installed.

I had to rename a few things, because a feature, a module and a crate that are all named "freetype" led to naming conflicts.

[Brooooooklyn]

see https://github.com/pcwalton/pathfinder/pull/70

[fschutt]

@Brooooooklyn I know, but I don't think that webrender will switch to a dynamically-linked approach. So I'd rather have freetype statically linked. I mean, servo already links against servo-freetype, so there isn't any benefit in dynamically linking freetype (from servos perspective). On the upside, nobody will have build issues anymore because their version of freetype is somehow wrong.

[pcwalton]

Just did this myself. Thanks!