pgsql: Simplify box_overlap computations.

Simplify box_overlap computations.

Given the assumption that a box's high coordinates are not less than its
low coordinates, the tests in box_ov() are overly complicated and can be
reduced to about half as much work. Since many other functions in
geo_ops.c rely on that assumption, there doesn't seem to be a good reason
not to use it here.

Per discussion of Alexander Korotkov's GiST fix, which was already using
the simplified logic (in a non-fuzzy form, but the equivalence holds just
as well for fuzzy).

Branch
------
master

Details
-------
http://git.postgresql.org/pg/commitdiff/f806c191a3d5faa1af1e5032d394fc6c5f93df86

Modified Files
--------------
src/backend/utils/adt/geo_ops.c | 13 ++++---------
1 files changed, 4 insertions(+), 9 deletions(-)