v4.27

update content

• linux aio backend almost complete rewritten to work around its limitations.
• epoll backend now mandatory for linux aio backend.
• fail assertions more aggressively on invalid fd's detected in the event loop, do not just silently fd_kill in case of user error.
• ev_io_start/ev_io_stop now verify the watcher fd using a syscall when EV_VERIFY is 2 or higher.

v4.25

add gitignore