val create : thread_safe_notify_signal_delivered:(unit -> unit)->t
create creates and returns a signal manager t. Whenever a signal that t is managing is delivered, it will call thread_safe_notify_signal_delivered from within the OCaml signal handler. Therefore thread_safe_notify_signal_delivered must be thread safe.
is_managing t signal returns true iff manage t signal has been called
type handler
install_handler t signals f causes t to manage the handling of signals, and registers f to run on every signal in signals that is delivered. It is an error if f ever raises when it is called.
remove_handler handler causes the particular handler to no longer handle the signals it was registered to handle. The signal manager continues to manage those signals, i.e. the OCaml signal handler remains installed, whether or not they still have handlers.