Linux: sync libevent/epoll.c to upstream's version.
Linux: sync libevent/epoll.c to upstream's version.

Our version of epoll.c has a bug where, when resizing an array,
pointers to the old array remain in kernel memory and are subsequently
used.

This is a pure cherry-pick from libevent 1.4.11-stable.

http://codereview.chromium.org/118124
BUG=11999


git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@17421 0039d316-1c4b-4281-b951-d872f2087c98

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