This provides a reliable and portable way to
test whether an environment variable is defined.
(Of course, if you are using glibc you may get
false positives if you include a = in the query.)
Signed-off-by: Mattias Andrée <maandree@kth.se>
The one specified by mdoc is hard to read for non-native
speakers from countries which read the date day-first (like
Germany, Greece, North-Korea, Swamp,...).
This is also consistent with how we generally specify dates
at suckless.org.
