S9 EXT  (sys:select list1 list2 list3)  ==>  integer | #f

Check whether any of the input file descriptors listed in LIST2
or output file descriptors listed in LIST3 are ready for reading
or writing respectively. Return the total number of file descriptors
that are ready. When no descriptors are ready at all, return #F.

LIST1 specifies the maximum time to wait for the file descriptors to
become ready. It is a two-element list with the following members:

        (seconds microseconds)

When '() is passed in the place of LIST1, SYS:SELECT will wait
indefinitely. When '(0 0) is passed to it, it will return immediately,
effectively implementing polling.

(sys:select '(0 0) '() '())  ==>  #f
