asio needs "poll" with timeout

[Gennady Proskurin <gpr@…>]

There were much of discussion about synchronous operations in asio with timeouts, bug #2832 for example. The main argument against it was difficulties with composed operations. I propose a compromise: some form of "poll" with timeout (poll_read/poll_write or something like that). I mean synchronous version of async_read_some(null_buffers()). If it will be implemented, it will be easy to write sync read with timeout, using combination of poll_read/read_some. I'm sure this "portable poll" will be very useful.