Will we ever raise _POSIX_VERSION ?

I notice that _POSIX_VERSION is still set to 200112L.  That's a shame,
because it prevents zstd from using utimensat and tzdata from using
strftime_l, even though we implement both of those functions.  And who
knows what programs in ports are keying off of it.  What would be
required for us to confidently raise it to 200809L or later?

-Alan