This patch creates a function named pg_get_triggerdef that takes the oid of
a trigger as its parameter. It is basically copied from the pg_dump code.
Once we're certain it's perfect, we could probably save some effort in
pg_dump by using the function.
Once it's committed, I will be modifying psql to show trigger definitions,
instead of just the name.
I have tested it with a bunch of different triggers, parameters, constraint
triggers, weird names, different functions, etc and it seems to be OK.
Cheers,
Chris
