GitLab

This error message will give information on what exactly has happened
and how to either solve ownership and permissions or disable the check
entirely.

Also gets rid of the purge of compinit caches since with the current
logic insecure completion directories are ignored and therefore haven't
tainted the cached files.

A new "lib/compfix.zsh" script defining a new handle_completion_insecurities()
function has been added, which handles insecure completion directories by
notifying users of said insecurities and moving away all existing completion
caches to a temporary directory. While intended to be called at startup, this
function is generally callable at any time (e.g., for testing).