[#2361] SslHandler.safeClose(...) may not notify the ChannelPromise

Motivation:
Native.epollCreate(...) fails on systems using a kernel < 2.6.27 / glibc < 2.9 because it uses epoll_create1(...) without checking if it is present

Modifications:
Check if epoll_create1(...) exists abd if not fall back to use epoll_create(...)

Result:
Works even on systems with kernel < 2.6.27 / glibc < 2.9