DirectWrite integration

[matprec]

@vvuk wrote Rust bindings for DirectWrite which some applications use internally, e.g. WR/Servo.
Currently, we're using wingdi for font enumeration, but DirectWrite has an interoperabillity interface for wingdi, but this part isn't ported yet.

ToDo:

• Enhance the gdi interop implementation in DirectWrite
• Adapt interface

[vvuk]

Do you actually need the GDI interop? If dwrite is available, it seems like the crate should fully use it and not go to GDI at all.

[matprec]

@vvuk Yes GDI interop is desired, as of the current state of winapi-rs bindings, one can't figure out whether or not a font is monospaced. For reference MSDN Docs and winapi-rs Docs.
Also, font loading from disk isn't implemented yet, so this would be the most easy way for us to maintain our interface.

I have the corresponding PR almost ready, expect it to come soon :)

[atouchet]

For reference the upstream dwrote repo is now located at: https://github.com/servo/dwrote-rs