Separate state from query string in pg_stat_activity
 
This separates the state (running/idle/idleintransaction etc) into
it's own field ("state"), and leaves the query field containing just
query text.
 
The query text will now mean "current query" when a query is running
and "last query" in other states. Accordingly,the field has been
renamed from current_query to query.
 
Since backwards compatibility was broken anyway to make that, the procpid
field has also been renamed to pid - along with the same field in
pg_stat_replication for consistency.
 
Scott Mead and Magnus Hagander, review work from Greg Smith