support H packet

[tromey]

The H packet is needed to set state for other packets.

It's easy enough to parse and forward to the handlers; but I wonder if it would make sense to either provide a mixin that handles the state management; or to handle the state directly in the implementation.

[tromey]

I think only Hg is needed, the other H packets are obsoleted by vCont.

[luser]

It's easy enough to parse and forward to the handlers; but I wonder if it would make sense to either provide a mixin that handles the state management; or to handle the state directly in the implementation.

I don't have strong feelings here, but I guess if it's just a bit of state then there's no reason we couldn't have this crate store the current thread, and any command that operates on the current thread could just have a Handler method that takes a thread parameter, to which we'd pass the current thread. Probably the only weirdness here would be "what's the default current thread?" If there's a sensible answer there, then that seems workable.

[tromey]

Since we need Hc after all (for bc and bs), and since I think it's best to have just one "continue" method on Handler, I think it would be best to keep the state locally so that these cases can be unified with vCont.