[COMMITTERS] pgsql: Further patch rangetypes_selfuncs.c's statistics slotmanagement

Further patch rangetypes_selfuncs.c's statistics slot management.

Values in a STATISTIC_KIND_RANGE_LENGTH_HISTOGRAM slot are float8,
not of the type of the column the statistics are for.

This bug is at least partly the fault of sloppy specification comments
for get_attstatsslot()/free_attstatsslot(): the type OID they want is that
of the stavalues entries, not of the underlying column.  (I double-checked
other callers and they seem to get this right.)  Adjust the comments to be
more correct.

Per buildfarm.

Security: CVE-2017-7484

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/da0759600664439238fe25fa84b1f0059bfdcdd6

Modified Files
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src/backend/utils/adt/rangetypes_selfuncs.c | 14 ++++++++------
src/backend/utils/cache/lsyscache.c         |  9 +++++----
src/include/catalog/pg_statistic.h          |  2 +-
3 files changed, 14 insertions(+), 11 deletions(-)