array_agg for 8.3

Hi,

Can anyone comment on the practicality of using the code for array_agg
from the dev repos, file src/backend/utils/adt/array_userfuncs.c in 8.3 as
a user defined function? It looks like this code was recently added, Nov
13th/14th. There are two functions, array_agg_transfn and
array_agg_finalfn, but I'm not clear how to use them. The idea would be to
compile and load them like as any other user-defined C function in 8.3. I
was informed that directly trying to use these functions in 8.3 would not
work. I realise this funcionality will be available in 8.4, but I don't
want to wait.

If anyone has working code along these lines, please send it to me. Also,
please CC me on any reply. Thanks.

Regards, Faheem Mitha.