Implement an "end script execution" feature

[JoaaoVerona]

Right now, there is no way to totally end a script execution. This proposal is to implement a feature which lets end the script execution and all of it's created asynchronous containers.

Definition:

end

or

end()

(see below)

Things to note:

• Should this be a component or a function? Although it seems more logical to have it as a function, have in mind that similar features, like break and continue are treated as components.

Example usage:

using std

println("Reading signals...")

while true {
  signal = readSignal()

  if signal == 0 {
    exit # OR exit()
  }
  else {
    println("Signal: " + signal)
  }
}