pgsql: Fix problem with whole-row Vars referencing sub-select outputs,

Log Message:
-----------
Fix problem with whole-row Vars referencing sub-select outputs, per
example from Jim Dew. Add some simple regression tests, since this is
an area we seem to break regularly :-(

Modified Files:
--------------
pgsql/src/backend/executor:
execQual.c (r1.185 -> r1.186)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/executor/execQual.c.diff?r1=1.185&r2=1.186)
pgsql/src/test/regress/expected:
select.out (r1.13 -> r1.14)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/expected/select.out.diff?r1=1.13&r2=1.14)
pgsql/src/test/regress/sql:
select.sql (r1.9 -> r1.10)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/sql/select.sql.diff?r1=1.9&r2=1.10)