pgsql: Extend the geometric regression test cases a little.

Extend the geometric regression test cases a little.

Add another edge-case value to "point_tbl", and add a test for
the line(point, point) function.

Some of the behaviors exposed here are wrong, but the idea of
committing this separately is to memorialize what we were getting,
and to allow easier inspection of the behavior changes caused by
upcoming patches.

Kyotaro Horiguchi (line() test added by me)

Discussion: https://postgr.es/m/CAGf+fX70rWFOk5cd00uMfa__0yP+vtQg5ck7c2Onb-Yczp0URA@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/a45272b25d6fc8f96793623545fc1f836ac39d94

Modified Files
--------------
src/test/regress/expected/create_index.out |  22 +-
src/test/regress/expected/geometry.out     | 370 ++++++++++++++++++++++++++---
src/test/regress/expected/point.out        | 138 +++++++----
src/test/regress/sql/geometry.sql          |   4 +
src/test/regress/sql/point.sql             |   2 +
5 files changed, 453 insertions(+), 83 deletions(-)