Log Message:
squid6: update to 6.6

Changes since 6.5:
        - Bug 5328: Fix ESI build with libxml2 v2.12.0
        - Bug 5319: QOS Netfilter MARK preservation is always disabled
        - Bug 5318: peer_digest.cc:399: "fetch->pd && \ 
receivedData.data"
        - Bug 5317: FATAL attempt to read data from memory
        - Bug 5154: Do not open IPv6 sockets when IPv6 is disabled
        - FTP: Ignore credentials with a NUL-prefixed username
        - log_db_daemon: Fix DSN construction
        - Limit the number of allowed X-Forwarded-For hops
        - Do not update StoreEntry expiration after errorAppendEntry()
        - improve handling of response sending errors