pgsql: Rename CHECKPOINT_IMMEDIATE to CHECKPOINT_FAST.

Rename CHECKPOINT_IMMEDIATE to CHECKPOINT_FAST.

The new name more accurately reflects the effects of this flag on a
requested checkpoint. Checkpoint-related log messages (i.e., those
controlled by the log_checkpoints configuration parameter) will now
say "fast" instead of "immediate", too. Likewise, references to
"immediate" checkpoints in the documentation have been updated to
say "fast". This is preparatory work for a follow-up commit that
will add a MODE option to the CHECKPOINT command.

Author: Christoph Berg <myon(at)debian(dot)org>
Discussion: https://postgr.es/m/aDnaKTEf-0dLiEfz%40msg.df7cb.de

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/bb938e2c3c7a955090f8b68b5bf75d064f6a36a0

Modified Files
--------------
doc/src/sgml/backup.sgml | 2 +-
doc/src/sgml/func.sgml | 2 +-
doc/src/sgml/ref/checkpoint.sgml | 2 +-
doc/src/sgml/ref/pg_basebackup.sgml | 3 ++-
src/backend/access/transam/xlog.c | 25 ++++++++++++------------
src/backend/commands/dbcommands.c | 10 +++++-----
src/backend/commands/tablespace.c | 2 +-
src/backend/postmaster/checkpointer.c | 24 +++++++++++------------
src/backend/storage/buffer/bufmgr.c | 4 ++--
src/backend/tcop/utility.c | 2 +-
src/include/access/xlog.h | 2 +-
src/test/recovery/t/041_checkpoint_at_promote.pl | 2 +-
12 files changed, 40 insertions(+), 40 deletions(-)