Update squid.inc

Fix missing last error language directory
Merge pull request #447 from thuynguyenduc/patch-1

Update squid.inc
squid3-dev - include antivirus depend packages to pkg_config
squid3-dev - improve icap antivirus integration code.
Merge remote-tracking branch 'upstream/master'
Add code to honor $pkg_interface flag for console mode.
Fix XMLRPC Sync code to prevent errors from bad return value.