improve proformance, such as ff_hook_writev(), ff_hook_ioctl(), ff_hook_setsockopt(), etc.
But there are some others socket API not support this now, such as
ff_hook_recvmsg(), ff_hook_readv(), ff_hook_sendmsg, because it not be
used now, and do it is relatively troublesome, So If you need call them
very frequently, maybe you should support it, and can see
ff_hook_writev().
Now it will cause memory lead, need to fix it later.
1. Add FF_KERNEL_EVENT argument, default disable. If enable FF_KERNEL_EVENT, epoll_create/epoll_clt/epoll_wait always call f-stack and system API at the same time. Use for some scenarios similar to Nginx. And F-Stack's kern.maxfiles value shoudn't > 65536.
2. Fix the issue that abs_timeout possibly is negative numbers.
3. If timeout < 0, such as -1, ff_hook_epoll_wait will run loop always until return some events.
3. Add some log.
fengbojiang