BUGFIX: Fix compilation on systems with EPOLLRDHUP undefined.

Since epolltable-internal.h uses this define, it must be defined before that is included.
Stop checking for inet_aton; we don't use it.

We had cmake and autoconf tests for the inet_aton function... but we
never actually use it any more.

(The autoconf tests still use the callability of inet_aton to decide
whether we need to link against -lresolv)

Reported by Harlan Stenn.
Merge pull request #97 from JoakimSoderberg/openwrt_fixes

BUGFIX: Fix compilation on systems with EPOLLRDHUP undefined.
Do not offer EV_FEATURE_EARLY_CLOSE if we have no EPOLLRDHUP