Log Message:
Update to libevent-2.0.10.
Supposedly API backwards-compatible with libevent 1.x.
Will need a recursive revbump for shlib name changes, though.

All regression tests pass except "thread_conditions_simple". Not sure
why yet, but it's new API so shouldn't break anything existing in pkgsrc
today.

Changes in libevent 2.0 include cleaner interfaces, buffered I/O improvements,
improved multithreading and openssl integration.