Have an HTTP server working on bare metal

[tomaka]

• Make core compile in no-std environments (Cannot define async fn with no_std rust-lang/rust#56974).
• Remove hosted TCP handler and replace with native TCP/IP implementation #52
• Add a native x86/x64 implementation of the time interface #56
• Implement a ne2000 driver #65

After that, we will have the time and tcp interfaces available to programs, which makes it possible to run useful stuff.

[tomaka]

Having some way to understand what's going on (e.g. making println work) might also be a good idea.

[tomaka]

Another issue that needs tackling for making core compile for no_std: wasmi-labs/wasmi#204

[tomaka]

Closing as done 🚀

Opened #473 for the remaining issue.