pgsql: Add new to_reg* functions for error-free OID lookups.

Add new to_reg* functions for error-free OID lookups.

These functions won't throw an error if the object doesn't exist,
or if (for functions and operators) there's more than one matching
object.

Yugo Nagata and Nozomi Anzai, reviewed by Amit Khandekar, Marti
Raudsepp, Amit Kapila, and me.

Branch
------
master

Details
-------
http://git.postgresql.org/pg/commitdiff/0886fc6a5c75b294544263ea979b9cf6195407d9

Modified Files
--------------
doc/src/sgml/func.sgml                |   48 +++++++++
src/backend/catalog/namespace.c       |    6 +-
src/backend/parser/parse_oper.c       |    6 +-
src/backend/parser/parse_type.c       |   29 ++++-
src/backend/utils/adt/regproc.c       |  108 ++++++++++++++++++-
src/include/catalog/catversion.h      |    2 +-
src/include/catalog/namespace.h       |    3 +-
src/include/catalog/pg_proc.h         |    8 ++
src/include/parser/parse_type.h       |    2 +-
src/include/utils/builtins.h          |    4 +
src/pl/plperl/plperl.c                |    2 +-
src/pl/plpgsql/src/pl_gram.y          |    2 +-
src/pl/plpython/plpy_spi.c            |    2 +-
src/pl/tcl/pltcl.c                    |    2 +-
src/test/regress/expected/regproc.out |  188 +++++++++++++++++++++++++++++++++
src/test/regress/parallel_schedule    |    2 +-
src/test/regress/serial_schedule      |    1 +
src/test/regress/sql/regproc.sql      |   61 +++++++++++
18 files changed, 457 insertions(+), 19 deletions(-)