Use native POSIX polling syscalls to read input

[lvxnull]

This will decrease the amount of thread synchronization calls during input processing and memory usage by removing the dedicated input thread and moving input reading code into the main thread, in polling read mode(non-canon, VMIN and VTIME set to 0), as well as replace the manual, sleep based polling implementation with pselect. Because polling is now done by pselect, SIGUSR1 will be used as the interrupt flag.
Additionally, input will be read in chunks instead of character by character.

[aristocratos]

@lvxnull
This is great, have you tested it on all platforms?

But I do believe the interrupt flag will still be needed as a way to signal that the next call to Input::poll should immediately return false. Because the the new Input::interrupt function will only stop a currently ongoing call to Input::poll right?

[lvxnull]

@aristocratos
I tested on linux only.

the new Input::interrupt function will only stop a currently ongoing call to Input::poll right?

No, because SIGUSR1 is only unblocked during pselect, and when a blocked signal is raised it stays in a pending state until it's unblocked and then executes immediately.

[aristocratos]

No, because SIGUSR1 is only unblocked during pselect, and when a blocked signal is raised it stays in a pending state until it's unblocked and then executes immediately.

Neat 👍🏼

Nice improvement over the previous mess!

Will do some stability testing on all platforms when I've got some time.

[imwints]

Also is there a reason to use select() over poll()?

[lvxnull]

Yes. ppoll() doesn't seem to be supported on mac os x. select()s file descriptor limitations don't apply here since only stdin is polled.

[imwints]

Can you update the declaration of poll(timeout)?

[lvxnull]

done