The enum definition, the two string tables and the test all were using
different orders (and in case of the test even missed entries).
Let's unify this, and make sure we always use the same order. This
settles the confusion, and makes the order used for the unicode string
table the canonical one, adjusting the other lists to match it. And adds
the missing entries to the tets.
$TERM would generally be set if we're connected to a proper graphical terminal
emulator. In all other cases, in particular if $TERM is not set, we almost
certainly are not connected to something that can output emojis. In particular
the text console is unlikely to ever do it correctly.
So let's invert the check, and only write emojis if $TERM is set.
Fixes#25521.
These functions are used pretty much independently of locale, i.e. the
only info relevant is whether th locale is UTF-8 or not. Hence let's
give this its own pair of .c/.h files.
Lennart Poettering
OMOJOLA JOSHUA
Zbigniew Jędrzejewski-Szmek
Yu Watanabe