Fixes#288, but more-or-less as a side-effect.
The “mi” key in LS_COLORS was meant to be used for a missing link path, but it wasn’t really used like that. There was also a bug where control characters in a broken symlink’s path were assumed to be underlined, because that’s what happened in the default colour scheme, but this assumption doesn’t hold when colours were disabled.
The solution to these was not to introduce another configurable colour code, but to start using _overlays_ to alter a bunch of colours at once. The “mi” code will have to be added back later.
This commit adds to the parsing of the LS_COLORS and EXA_COLORS variables so that non-two-letter codes (keys other than things like ‘di’ or ‘ln’ or ‘ex’) will be treated as file name globs, and get used to colour files accordingly.
Fixes#116 for good.
