Strictly speaking, we should check with the SSIDEncoding value sent out
by the station, as specified in the 2012 version of 802.11 (page 566),
but wpa_supplicant does not (yet) expose this information and stations
may not set the field to UTF-8 and still encode their SSID accordingly.

We therefore assume SSIDs to be UTF-8 encoded (the only real alternative
is treating SSIDs as raw byte string) in wifi-menu. Note that wifi-menu
is only provided as a convenience and many/most use cases involve
writing profile files manually.

When the current character map is not set to UTF-8, wifi-menu will only
use ASCII characters in its screen output.
This can be forced using for example `LC_CTYPE=C wifi-menu`.

Thanks to Declspeck <declspeck@declblog.com> for their activity on the
Flyspray task.