Obey the LANGUAGE environment variable (if set), which is GNU
gettext's primary way of determining language preference. Apparently
ignored by wx until now, even though wx attempts to be a
reimplementation of GNU gettext.
The LANGUAGE variable may contain a list of preferred languages,
so use that list to find the best translation.
GNU gettext has supported multiple preferred languages since forever
(at least 15 years), and therefore it is odd that this wasn't already
implemented in 01f953efb2. Instead,
it was implied that Unix does not support such. (Even if GNU is not
Unix, nothing stops a wxWidgets app supporting such nevertheless.)
Closes https://github.com/wxWidgets/wxWidgets/pull/948
829f181ccd