If there is an event-config.h in include/event2 (either because we
screwed up packaging like in 2.0.6-rc or because we previously tried
building with mingw and we didn't make distclean in the middle), we
want MSVC to find the one one in WIN32-Code/include/event2 first.
Found by Gilad Benjamini.
The entry points are evutil_getaddrinfo and evdns_getaddrinfo respectively.
There are fairly extensive unit tests.
I believe this code conforms to RFC3493 pretty closely, but there are
probably more issues. It should get tested on more platforms.
This code means we can dump the well-intentioned but weirdly-implemented
bufferevent_evdns and evutil_resolve code.
svn:r1537
