WIP: use cargo-c

[elmarco]

Use https://github.com/lu-zero/cargo-c to build a C library.

It handles C libraries and .pc file generation, as well as some installation details. However, header generation is done manually in build.rs now (still with the gobject cbindgen fork)

Depends on #6

[thiblahute]

I played a bit with this branch and moved to using meson instead of Makefile to see how we could integrate GObject based libs written in rust into existing projects: https://github.com/thiblahute/gobject-example-rs/commits/cargoc%2Bmeson (Added a minor fix to cbindgen after rebasing this branch).

[sdroege]

That's great :)