bufferevent_pair: don't call downcast(NULL)
Add -Qunused-arguments for clang on macos

The clang compiler provided with macosx emits warnings like:

  CC       bufferevent.lo
clang: warning: argument unused during compilation: '-I .'
clang: warning: argument unused during compilation: '-I ./compat'
clang: warning: argument unused during compilation: '-I ./include'
clang: warning: argument unused during compilation: '-I ./include'

for each file being compiled. This generates a lot of noise during
compilation making it hard to see "real" errors. This patch mute
those warnings.
Fix a crash in evdns related to shutting down evdns

Patch from YASUOKA Masahiko; fix for libevent github issue #113.
Fix a crash in evdns related to shutting down evdns

(Improved version to deal correctly with probe requests)

Patch from YASUOKA Masahiko; fix for libevent github issue #113.
Add a few files created by "make verify" to .gitignore.
Use FindClose for handle from FindFirstFile in http-server.c

Noted by Miles Chan as issue #145
Consistently check for failure from evbuffer_pullup()

Closes issue #148.
regress_buffer: fix 'memcmp' compare size
[Bugfix] fix bufferevent setwatermark suspend_read
Fix a typo in a doxygen comment. Reported by 亦得.
Fix race caused by event_active

There is a race between manual event_active and natural event activation. If both happen at the same time on the same FD, they would both be protected by the same event base lock except for 1 LoC where the fields of struct event are read without any kind of lock. This commit does those reads into local variables inside the lock and then invokes the callback with those local arguments outside the lock. In 2.0-stable, none of this is inside the lock; in HEAD, only the callback is read inside the lock. This gets the callback and all 3 arguments inside the lock before calling it outside the lock.
Work on the changelog for 2.0.22
Merge branch 'patches-2.0' of github.com:libevent/libevent into patches-2.0