"Functions and trigger procedures cannot start or commit transactions"

It says in the Postgres docs for 7.0, "Functions and trigger
procedures cannot start or commit transactions and Postgres does not
have nested transactions."

Will it be possible for functions to start or commit transactions in
7.1? This would be an extremely useful feature to me. I'm trying to
get all of my operations written as pl/pgsql functions, but somethings
need to do transactions so they can do row-level locking. Maybe I'll
have to do that outside the function, though.

Thanks