Log Message:
Changes 4.22:
- when epoll detects unremovable fds in the fd set, rebuild
  only the epoll descriptor, not the signal pipe, to avoid
  SIGPIPE in ev_async_send. This doesn't solve it on fork,
  so document what needs to be done in ev_loop_fork
- remove superfluous sys/timeb.h include on win32
- updated libecb.