Low-level bindings to the OpenDHT C library

Building opendht-sys

Steps we take

1. pkg-config is used to find the opendht-c library on the current system.
2. cmake is tried next with the opendht source in ./vendor/opendht.

Build Requirements

If we build via cmake, we need the following installed first (Debian or Ubuntu):

• fmt-dev
• pkg-config
• libgnutls28-dev - yes, on crates.io
• libmsgpack-dev - no
• libargon2-dev - yes, on crates.io
• libasio-dev - no
• libfmt-dev - no, needed?
• nettle-dev - yes, on crates.io
• ninja-build

-sys crates

TODO: All of the above will be -sys crates and set as dependencies in our Cargo.toml file.