pgsql: Change PROCEDURE to FUNCTION in CREATE OPERATOR syntax

Change PROCEDURE to FUNCTION in CREATE OPERATOR syntax

Since procedures are now a different thing from functions, change the
CREATE OPERATOR syntax to use FUNCTION in the clause that specifies the
function. PROCEDURE is still accepted for compatibility.

Reported-by: Peter Geoghegan <pg(at)bowt(dot)ie>
Reviewed-by: Jonathan S. Katz <jonathan(dot)katz(at)excoventures(dot)com>

Branch
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REL_11_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/fd4417e8ac46ea4cb079ed53f849dc48199506d6

Modified Files
--------------
doc/src/sgml/extend.sgml | 2 +-
doc/src/sgml/ref/create_operator.sgml | 12 ++++++++++--
doc/src/sgml/xoper.sgml | 4 ++--
src/backend/commands/operatorcmds.c | 20 ++++++++++++--------
src/bin/pg_dump/pg_dump.c | 2 +-
src/test/regress/expected/create_operator.out | 6 +++---
src/test/regress/sql/create_operator.sql | 2 +-
7 files changed, 30 insertions(+), 18 deletions(-)