pgsql: Rewrite pg_size_pretty() to avoid compiler bug.

Rewrite pg_size_pretty() to avoid compiler bug.

Convert it to use successive shifts right instead of increasing a divisor.
This is probably a tad more efficient than the original coding, and it's
nicer-looking than the previous patch because we don't need a special case
to avoid overflow in the last branch. But the real reason to do it is to
avoid a Solaris compiler bug, as per results from buildfarm member moa.

Branch
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REL8_4_STABLE

Details
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http://git.postgresql.org/pg/commitdiff/c5459735fd4d5ec8ea5ebfcd5dec03548d9ac8d4

Modified Files
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src/backend/utils/adt/dbsize.c | 32 +++++++++++++-------------------
1 files changed, 13 insertions(+), 19 deletions(-)