pgsql: Code review for auto-tuned effective_cache_size.

Code review for auto-tuned effective_cache_size.

Fix integer overflow issue noted by Magnus Hagander, as well as a bunch
of other infelicities in commit ee1e5662d8d8330726eaef7d3110cb7add24d058
and its unreasonably large number of followups.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/2850896961994aa0993b9e2ed79a209750181b8a

Modified Files
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doc/src/sgml/config.sgml | 28 +++----
src/backend/optimizer/path/costsize.c | 106 ++++++++++++++-----------
src/backend/postmaster/postmaster.c | 1 -
src/backend/utils/misc/guc.c | 1 +
src/backend/utils/misc/postgresql.conf.sample | 2 +-
src/include/optimizer/cost.h | 2 -
src/include/utils/guc.h | 4 +-
7 files changed, 77 insertions(+), 67 deletions(-)