pgsql: Remove zero- and one-argument range constructor functions.

Remove zero- and one-argument range constructor functions.

Per discussion, the zero-argument forms aren't really worth the catalog
space (just write 'empty' instead).  The one-argument forms have some use,
but they also have a serious problem with looking too much like functional
cast notation; to the point where in many real use-cases, the parser would
misinterpret what was wanted.

Committing this as a separate patch, with the thought that we might want
to revert part or all of it if we can think of some way around the cast
ambiguity.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/df73584431e7edb1dd76578777bd0fcc17b916a1

Modified Files
--------------
doc/src/sgml/rangetypes.sgml             |   20 +++-------
src/backend/commands/typecmds.c          |    6 +--
src/backend/utils/adt/rangetypes.c       |   58 ------------------------------
src/include/catalog/catversion.h         |    2 +-
src/include/catalog/pg_proc.h            |   24 ------------
src/include/utils/rangetypes.h           |    3 --
src/test/regress/expected/rangetypes.out |   16 ++++----
src/test/regress/sql/rangetypes.sql      |   14 ++++----
8 files changed, 24 insertions(+), 119 deletions(-)