Proxy: fixed proxy_method to always add space.

Before the patch if proxy_method was specified at http{} level the code
to add trailing space wasn't executed, resulting in incorrect requests
to upstream.
Configure: fixed style of include directories.
Configure: fixed GeoIP library detection.
GeoIP: IPv6 support.

When using IPv6 databases, IPv4 addresses are looked up as IPv4-mapped
IPv6 addresses.

Mostly based on a patch by Gregor Kališnik (ticket #250).
Events: fixed null pointer dereference with resolver and poll.

A POLLERR signalled by poll() without POLLIN/POLLOUT, as seen on
Linux, would generate both read and write events, but there's no
write event handler for resolver events.  A fix is to only call
event handler of an active event.