Chris Davis points out that GetQueuedCompletionStatus
sometimes returns false not to report "No events for
you!" but instead to report "An overlapped operation
failed." Add a way to tell an event_overlapped that
its operation failed.
svn:r1490
OpenSSL uses something like this to implement get/set access for
properties on its BIOs, so that it doesn't need to add a pair of
get/set functions to the vtable struct for every new abstract property
it provides an accessor for.
Doing this lets us make bufferevent_setfd abstract, and implement an
abstract bufferevent_getfd.
svn:r1284
Either I need to make the callbacks get deferred in a base with no events (doable), or I need to make it okay to call launch_read from inside the callback for read (tricky).
svn:r1277
