pgsql: Separate state from query string in pg_stat_activity

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

Branch
------
master

Details
-------
http://git.postgresql.org/pg/commitdiff/4f42b546fd87a80be30c53a0f2c897acb826ad52

Modified Files
--------------
doc/src/sgml/monitoring.sgml         |  233 ++++++++++++++++++++++++++++++++--
src/backend/catalog/system_views.sql |   10 +-
src/backend/postmaster/autovacuum.c  |    2 +-
src/backend/postmaster/pgstat.c      |   55 +++++++--
src/backend/tcop/postgres.c          |   16 +-
src/backend/utils/adt/pgstatfuncs.c  |  116 +++++++++++------
src/include/catalog/catversion.h     |    2 +-
src/include/catalog/pg_proc.h        |    4 +-
src/include/pgstat.h                 |   21 +++-
src/test/regress/expected/rules.out  |    4 +-
10 files changed, 378 insertions(+), 85 deletions(-)