MFH: r391999

Release pkg 1.5.5
Changes:

• Manpages updates
• Add a random delay to pkg-audit when invoked without a TTY
• Update zsh completion
• Add a new AUTOCLEAN option to automatically clean the cache directory
• Don't attempt to set file ownership when INSTALL_AS_USER is set
• Add a new configuration item to define custom HTTP User-Agent
• Fix an integer overflow when displaying package size for packages larger than 2GiB.

Approved by: portmgr (implicit)