pgsql: Make fast promotion the default promotion mode.

Make fast promotion the default promotion mode.
Continue to allow a request for synchronous
checkpoints as a mechanism in case of problems.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/2317a63328cd9d1c22d02218c6959f340b63d98f

Modified Files
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src/backend/access/transam/xlog.c |   15 ++-------------
src/bin/pg_ctl/pg_ctl.c           |   17 ++++++-----------
2 files changed, 8 insertions(+), 24 deletions(-)