Bikeshed invitation for nl_langinfo ambiguities

[Rich Felker <dalias@libc.org>]

I've found 2 ambiguous-string-to-translate bugs in musl's locale
support in nl_langinfo: The pairs ABMON_5 and MON_5 ("May"), and T_FMT
and ERA_T_FMT ("%H:%M:%S"), have the same values in the C locale, and
thus can't be translated to distinct values like they need to be in
other locales.

Any opinions on the cleanest way to handle this? There are various
hacks I could do at the implementation level, like adding a prefix
character to one or the other then applying +1 to the output string,
But whatever solution we choose becomes a public interface for
translators, so it should be something that's not horribly ugly.

So.... it's bikeshed time.

Rich