pgsql: Revert ill-considered change of index-size fudge factor.

Revert ill-considered change of index-size fudge factor.

This partially reverts commit 21a39de5809cd3050a37d2554323cc1d0cbeed9d,
restoring the pre-9.2 cost estimates for index usage.  That change
introduced much too large a bias against larger indexes, as per reports
from Jeff Janes and others.  The whole thing needs a rewrite, which I've
done in HEAD, but the safest thing to do in 9.2 is just to undo this
multiplier change.

Branch
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REL9_2_STABLE

Details
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http://git.postgresql.org/pg/commitdiff/3e9960e9d935e7e7c12e78441f99befc877563ef

Modified Files
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src/backend/utils/adt/selfuncs.c |    4 ++--
1 files changed, 2 insertions(+), 2 deletions(-)