Fix needless bufferevent includes in evdns.c
Remove unneeded declaration in bufferevent-internal.h
Add access to max event count stats

This commit provides an interface for accessing and resetting the maximum
number of events in a given period.  This information provides better insight
into event queue pressure.
Fixed bug using wrong variable in max event compare
Added unit test for max event counts
Provide on request complete callback facility

This patch provides the ability to receive a callback on the completion of a
request.  The callback takes place immediately before the request's resources
are released.
Merge remote-tracking branch 'asweeny86/event-count-max'
evhttp_request_set_on_complete_cb to be more specific about what the function actually does and usage
Update unit test to make sure that the callback happens after the output data is written
Merge remote-tracking branch 'asweeny86/on-complete-cb'
Fix a pile of coverity warnings in the unit tests

Most of these problems can only trigger when the tests fail, but it's
good hygiene to keep the code warning-free in any case.
Fix coverity warnings in benchmark tools.

Again, not harmful, but best to stay warning-free.
Whoops; fix compilation in bench.c
Remove spurious checks in evrpc.c error cases (coverity)

Coverity hates the case where you have a redundant NULL check after
using something.
Fix a couple of compilation warnings in regress_http.c
Fix even more coverity warnings.