Lots of work to make iocp work again.

Big issue with IOCP vs. poll variants is that the overlapped
structures have a longer lifetime than intermediate state needed
for epoll. One cannot free overlapped structures after closing a
handle/socket, like one can do with any intermediate state when using
readiness-based IO.

test/helper.janet

@@ -42,9 +42,6 @@
   (set suite-name
        (cond
          (number? x) (string x)
-         (string? x) (string/slice x
-                                   (length "test/suite-")
-                                   (- (inc (length ".janet"))))
          (string x)))
   (set start-time (os/clock))
   (eprint "Starting suite " suite-name "..."))