pgsql: Add string functions: concat(), concat_ws(), left(), right(), and

Log Message:
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Add string functions: concat(), concat_ws(), left(), right(), and reverse().

Pavel Stehule, reviewed by me.

Modified Files:
--------------
pgsql/doc/src/sgml:
func.sgml (r1.529 -> r1.530)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/func.sgml?r1=1.529&r2=1.530)
pgsql/src/backend/utils/adt:
varlena.c (r1.179 -> r1.180)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/adt/varlena.c?r1=1.179&r2=1.180)
pgsql/src/include/catalog:
catversion.h (r1.596 -> r1.597)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/catversion.h?r1=1.596&r2=1.597)
pg_proc.h (r1.580 -> r1.581)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/pg_proc.h?r1=1.580&r2=1.581)
pgsql/src/include/utils:
builtins.h (r1.354 -> r1.355)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/utils/builtins.h?r1=1.354&r2=1.355)
pgsql/src/test/regress/expected:
text.out (r1.4 -> r1.5)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/expected/text.out?r1=1.4&r2=1.5)
pgsql/src/test/regress/sql:
text.sql (r1.4 -> r1.5)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/sql/text.sql?r1=1.4&r2=1.5)