pgsql: Improve contrib/cube's handling of zero-D cubes, infinities, and

Improve contrib/cube's handling of zero-D cubes, infinities, and NaNs.

It's always been possible to create a zero-dimensional cube by converting
from a zero-length float8 array, but cube_in failed to accept the '()'
representation that cube_out produced for that case, resulting in a
dump/reload hazard. Make it accept the case. Also fix a couple of
other places that didn't behave sanely for zero-dimensional cubes:
cube_size would produce 1.0 when surely the answer should be 0.0,
and g_cube_distance risked a divide-by-zero failure.

Likewise, it's always been possible to create cubes containing float8
infinity or NaN coordinate values, but cube_in couldn't parse such input,
and cube_out produced platform-dependent spellings of the values. Convert
them to use float8in_internal and float8out_internal so that the behavior
will be the same as for float8, as we recently did for the core geometric
types (cf commit 50861cd68). As in that commit, I don't pretend that this
patch fixes all insane corner-case behaviors that may exist for NaNs, but
it's a step forward.

(This change allows removal of the separate cube_1.out and cube_3.out
expected-files, as the platform dependency that previously required them
is now gone: an underflowing coordinate value will now produce an error
not plus or minus zero.)

Make errors from cube_in follow project conventions as to spelling
("invalid input syntax for cube" not "bad cube representation")
and errcode (INVALID_TEXT_REPRESENTATION not SYNTAX_ERROR).

Also a few marginal code cleanups and comment improvements.

Tom Lane, reviewed by Amul Sul

Discussion: <15085(dot)1472494782(at)sss(dot)pgh(dot)pa(dot)us>

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/f31a931fade868d788ef4480c59753a2d5059246

Modified Files
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contrib/cube/cube.c | 70 +-
contrib/cube/cubedata.h | 7 +
contrib/cube/cubeparse.y | 148 ++--
contrib/cube/cubescan.l | 15 +-
contrib/cube/expected/cube.out | 115 ++-
contrib/cube/expected/cube_1.out | 1710 --------------------------------------
contrib/cube/expected/cube_2.out | 115 ++-
contrib/cube/expected/cube_3.out | 1710 --------------------------------------
contrib/cube/sql/cube.sql | 11 +-
9 files changed, 275 insertions(+), 3626 deletions(-)