pgsql: Allow the syntax CREATE TYPE foo, with no parameters, to permit

Log Message:
-----------
Allow the syntax CREATE TYPE foo, with no parameters, to permit explicit
creation of a shell type. This allows a less hacky way of dealing with
the mutual dependency between a datatype and its I/O functions: make a
shell type, then make the functions, then define the datatype fully.
We should fix pg_dump to handle things this way, but this commit just deals
with the backend.

Martijn van Oosterhout, with some corrections by Tom Lane.

Modified Files:
--------------
pgsql/doc/src/sgml/ref:
create_type.sgml (r1.60 -> r1.61)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/ref/create_type.sgml.diff?r1=1.60&r2=1.61)
pgsql/doc/src/sgml:
xtypes.sgml (r1.25 -> r1.26)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/xtypes.sgml.diff?r1=1.25&r2=1.26)
pgsql/src/backend/catalog:
pg_type.c (r1.104 -> r1.105)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/catalog/pg_type.c.diff?r1=1.104&r2=1.105)
pgsql/src/backend/commands:
typecmds.c (r1.86 -> r1.87)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/typecmds.c.diff?r1=1.86&r2=1.87)
pgsql/src/backend/parser:
gram.y (r2.530 -> r2.531)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/parser/gram.y.diff?r1=2.530&r2=2.531)
pgsql/src/backend/utils/adt:
pseudotypes.c (r1.15 -> r1.16)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/adt/pseudotypes.c.diff?r1=1.15&r2=1.16)
pgsql/src/include/catalog:
catversion.h (r1.316 -> r1.317)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/catversion.h.diff?r1=1.316&r2=1.317)
pg_operator.h (r1.140 -> r1.141)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/pg_operator.h.diff?r1=1.140&r2=1.141)
pg_proc.h (r1.398 -> r1.399)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/pg_proc.h.diff?r1=1.398&r2=1.399)
pgsql/src/include/utils:
builtins.h (r1.274 -> r1.275)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/utils/builtins.h.diff?r1=1.274&r2=1.275)
pgsql/src/test/regress/expected:
create_type.out (r1.12 -> r1.13)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/expected/create_type.out.diff?r1=1.12&r2=1.13)
pgsql/src/test/regress/sql:
create_type.sql (r1.8 -> r1.9)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/sql/create_type.sql.diff?r1=1.8&r2=1.9)