Would it be possible to add functions to tab-completion in psql?

[hubert depesz lubaczewski]

Hi,
As a dba I have to, very often, query system functions, starting with
pg_last_xact_replay_timestamp and pg_current_wal_lsn.

Would it be possible/hard/expensive, to change tab-completion so that:

select pg_<tab> would work?

Best regards,

depesz