chore: use freetype to replace freetype-sys

[Brooooooklyn]

I'm trying to build a node canvas with rust: context_2d, and borrowed tones of codes from servo.

When I was trying to built it on linux, it crashed with:

error: multiple packages link to native library `freetype`, but a native library can be linked only once

package `servo-freetype-sys v4.0.3`
    ... which is depended on by `azure v0.25.0`
    ... which is depended on by `rustcanvas v0.1.0 (file:///Users/longyinan/workspace/Github/rust-canvas)`
links to native library `freetype`

package `freetype-sys v0.6.0`
    ... which is depended on by `pathfinder_font_renderer v0.1.0 (https://github.com/rust-canvas/pathfinder?branch=rust-canvas#5f082aa4)`
    ... which is depended on by `rustcanvas v0.1.0 (file:///Users/longyinan/workspace/Github/rust-canvas)`
also links to native library `freetype`

So I change the dependencies in pathfinder to pass the compile, and I have no idea about the differences between the freetype-sys & freetype.

Please tell me if you think this Pull Request is unreasonable, and feel free to close it.

[messense]

It fails to compile because freetype-sys specified links key in its Cargo.toml which is sensible IMO.

[Brooooooklyn]

Yes, I know what caused built failed, what I don't understand is, what's the differences between the freetype-sys & freetype.

[messense]

I think the differences is that freetype-sys only dynamically links to libfreetype2 installed on your system, while freetype by default depends on servo-freetype-sys which bundles libfreetype2 source code and links to it statically.

[pcwalton]

I'm a bit confused as to what's going on with this PR.

[Brooooooklyn]

ehh.. it's just make pathfinder work with rust-azure

[pcwalton]

I'm going to go ahead and close this in favor of the current dynamic linking behavior, but feel free to reopen if a better solution is found.