Rewrite Windows poll()

We can now await signals, files, pipes, and console simultaneously. This
change also gives a deeper review and testing to changes made yesterday.

libc/calls/ppoll.c

@@ -90,8 +90,11 @@
  *     was determined about the file descriptor
  * @param timeout if null will block indefinitely
  * @param sigmask may be null in which case no mask change happens
- * @raise E2BIG if we exceeded the 64 socket limit on Windows
+ * @raise EINVAL if we exceeded the 64 socket limit on Windows
  * @raise ECANCELED if thread was cancelled in masked mode
+ * @raise EINVAL if `nfds` exceeded `RLIMIT_NOFILE`
+ * @raise ENOMEM on failure to allocate memory
+ * @raise EINVAL if `*timeout` is invalid
  * @raise EINTR if signal was delivered
  * @cancelationpoint
  * @asyncsignalsafe
@@ -104,6 +107,10 @@ int ppoll(struct pollfd *fds, size_t nfds, const struct timespec *timeout,
   struct timespec ts, *tsp;
   BEGIN_CANCELATION_POINT;
 
+  // validate timeout
+  if (timeout && timeout->tv_nsec >= 1000000000)
+    return einval();
+
   // The OpenBSD poll() man pages claims it'll ignore POLLERR, POLLHUP,
   // and POLLNVAL in pollfd::events except it doesn't actually do this.
   size_t bytes = 0;