pgsql: Code and docs review for cube kNN support.

Code and docs review for cube kNN support.

Commit 33bd250f6c4cc309f4eeb657da80f1e7743b3e5c could have done with
some more review:

Adjust coding so that compilers unfamiliar with elog/ereport don't complain
about uninitialized values.

Fix misuse of PG_GETARG_INT16 to retrieve arguments declared as "integer"
at the SQL level.  (This was evidently copied from cube_ll_coord and
cube_ur_coord, but those were wrong too.)

Fix non-style-guide-conforming error messages.

Fix underparenthesized if statements, which pgindent would have made a
hash of, and remove some unnecessary parens elsewhere.

Run pgindent over new code.

Revise documentation: repeated accretion of more operators without any
rethinking of the text already there had left things in a bit of a mess.
Merge all the cube operators into one table and adjust surrounding text
appropriately.

David Rowley and Tom Lane

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/81ee726d87ec67c4f2846110c99f72e8a20dcd07

Modified Files
--------------
contrib/cube/cube.c              |  128 ++++++++++++------------
contrib/cube/expected/cube.out   |   14 +--
contrib/cube/expected/cube_1.out |   14 +--
contrib/cube/expected/cube_2.out |   14 +--
contrib/cube/expected/cube_3.out |   14 +--
doc/src/sgml/cube.sgml           |  199 ++++++++++++++++++--------------------
6 files changed, 186 insertions(+), 197 deletions(-)