PAC: fill the server address with serving address

When usable. Rather than "listening ip".
'Cause when multiple network cards are used, "listening ip" can be wrong.
Merge pull request #20 from zwhfly/3.0

PAC: fill the server address with serving address
refine pagespeed
refine pagespeed
bugfix for pagespeed
improve dns resolve
bump version to 3.1.18
refine proxy.pac
Merge pull request #7 from goagent/3.0

update