This isn't really a "locale" variable as such. It has no effect on
encoding and stuff, it's just the output language.
What we really want here is get something better than the awkward "C"
or "POSIX" for LC_CTYPE specifically - everything else doesn't really
matter.
A common problem for users is that fish doesn't get a locale. This often
happens if systemd is used with getty and fish as login shell.
Fixes#277
Note that I (@krader) made editorial changes before merging this. For
example, running `make style` and otherwise changing long statements to a
series of shorter statements. So if there are any problems it is possible
I introduced them.
