pgsql: Implement IS NOT DISTINCT FROM, update the regression tests and - Mailing list pgsql-committers

Log Message:
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Implement IS NOT DISTINCT FROM, update the regression tests and docs.
Patch from Pavel Stehule, minor fixups by myself.

Modified Files:
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    pgsql/doc/src/sgml:
        func.sgml (r1.297 -> r1.298)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/func.sgml.diff?r1=1.297&r2=1.298)
    pgsql/src/backend/parser:
        gram.y (r2.516 -> r2.517)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/parser/gram.y.diff?r1=2.516&r2=2.517)
    pgsql/src/test/regress/expected:
        select_distinct.out (r1.4 -> r1.5)

(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/expected/select_distinct.out.diff?r1=1.4&r2=1.5)
    pgsql/src/test/regress/sql:
        select_distinct.sql (r1.4 -> r1.5)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/sql/select_distinct.sql.diff?r1=1.4&r2=1.5)