do-select FD set bytevector sizes

[Derick Eddington]

In ikarus.io.ss, in do-select, n is calculated to be (add1 (get-max-fd)), and the rbv, wbv, and xbv bytevectors' sizes are n, but I think their sizes could be (add1 (div (get-max-fd) 8)) in order to not allocate larger bytevectors than needed for the bit sets. Or, for even better performance, they could be allocated only once to FD_SETSIZE (I guess a foreign-call to get that) and zeroed on entry to do-select (but that's not multi-thread safe...).

[Derick Eddington (derick-eddington)]

But given how fast Ikarus's average allocation time is, probably the
difference between zeroing and allocating zeros is negligible?

[Abdulaziz Ghuloum (aghuloum)]

Fixed in 1502. Yes, it doesn't matter really how big it is.