pgsql: array_length() function, and for SQL compatibility also

Log Message:
-----------
array_length() function, and for SQL compatibility also cardinality()
function as a special case.

This version still has the suspicious behavior of returning null for an
empty array (rather than zero), but this may need a wholesale revision of
empty array behavior, currently under discussion.

Jim Nasby, Robert Haas, Peter Eisentraut

Modified Files:
--------------
pgsql/doc/src/sgml:
array.sgml (r1.67 -> r1.68)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/array.sgml?r1=1.67&r2=1.68)
func.sgml (r1.456 -> r1.457)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/func.sgml?r1=1.456&r2=1.457)
pgsql/src/backend/utils/adt:
arrayfuncs.c (r1.148 -> r1.149)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/adt/arrayfuncs.c?r1=1.148&r2=1.149)
pgsql/src/include/catalog:
catversion.h (r1.503 -> r1.504)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/catversion.h?r1=1.503&r2=1.504)
pg_proc.h (r1.524 -> r1.525)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/pg_proc.h?r1=1.524&r2=1.525)
pgsql/src/include/utils:
array.h (r1.69 -> r1.70)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/utils/array.h?r1=1.69&r2=1.70)
pgsql/src/test/regress/expected:
arrays.out (r1.42 -> r1.43)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/expected/arrays.out?r1=1.42&r2=1.43)
pgsql/src/test/regress/sql:
arrays.sql (r1.31 -> r1.32)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/sql/arrays.sql?r1=1.31&r2=1.32)