The `pkg-config` should query the `bash-completion` package instead of `bash-completions`.

I also think we should use `compatdir` instead of `completionsdir`. The new completionsdir has a slightly different behaviour where it dynamically loads things when the user tries to complete a command based on the name of the command, while the compatdir keeps the pre-1.99 behaviour. If we switch to completionsdir we should remove the `have()` command at the top of the completions file, or redefine it as it is no longer included in bash-completion (I'm not 100% sure if it exists for compatdir scripts).