pgsql: Add capability to suppress CONTEXT: messages to elog machinery.

Add capability to suppress CONTEXT: messages to elog machinery.

Hiding context messages usually is not a good idea - except for rather
verbose debugging/development utensils like LOG_DEBUG. There the
amount of repeated context messages just bloat the log without adding
information.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/570bd2b3fd20d3f8896f5e6a8133d6aed385ac86

Modified Files
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src/backend/utils/error/elog.c |   24 ++++++++++++++++++++++--
src/include/utils/elog.h       |    2 ++
2 files changed, 24 insertions(+), 2 deletions(-)