Timers

[archseer]

Timers includes:

• bif erlang:start_timer/3
• bif erlang:start_timer/4
• bif erlang:send_after/3
• bif erlang:send_after/4
• bif erlang:cancel_timer/1
• bif erlang:cancel_timer/2
• bif erlang:read_timer/1
• bif erlang:read_timer/2

As well as WaitTimeout and Send with timeout instructions. The implementation should use a hierarchical timing wheel, can probably base the implementation on https://github.com/tokio-rs/tokio/tree/master/tokio-timer/src/wheel

If we decide to integrate with Tokio for the async I/O (yields the BIF when blocking), we could avoid copying the impl. If we copy it, we probably want a new thread that will keep track of the wheel and schedule processes when their timers are up (similar to what process::spawn internals do)

[archseer]

Simple send_after was implemented, but no way to cancel or manipulate timers yet.