This keeps one central place for the XDG switch.  Specifically, this
disables the XDG listener on Apple, where XDG is not supported.

Changed listen_add_config_param() to use generic address parsing

Passing it by value is actually smaller (32 bit) than the rvalue
reference (64 bit pointer), and it ensures that the object is consumed
after the call returns, no matter how the methods are implemented.

Move code from config_parse_path().

Don't use global variables.