Following up something Pavel wrote, I notice that json_agg() and
json_object_agg() are both marked as immutable, even though they invoke
IO functions, while json_object is marked stable, even though it does
not, and can probably be marked as immutable. Mea maxima culpa.
I'm not sure what we should do about these things now. Is it a tragedy
if we let these escape into the 9.4 release that way?
cheers
andrew
