pgsql-server: Standardize on the assumption that the arguments of a

Log Message:
-----------
Standardize on the assumption that the arguments of a RowExpr correspond
to the physical layout of the rowtype, ie, there are dummy arguments
corresponding to any dropped columns in the rowtype. We formerly had a
couple of places that did it this way and several others that did not.
Fixes Gaetano Mendola's "cache lookup failed for type 0" bug of 5-Aug.

Modified Files:
--------------
pgsql-server/src/backend/executor:
execQual.c (r1.165 -> r1.166)
(http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/backend/executor/execQual.c.diff?r1=1.165&r2=1.166)
pgsql-server/src/backend/optimizer/util:
clauses.c (r1.177 -> r1.178)
(http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/backend/optimizer/util/clauses.c.diff?r1=1.177&r2=1.178)
pgsql-server/src/backend/parser:
parse_coerce.c (r2.119 -> r2.120)
(http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/backend/parser/parse_coerce.c.diff?r1=2.119&r2=2.120)
parse_relation.c (r1.96 -> r1.97)
(http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/backend/parser/parse_relation.c.diff?r1=1.96&r2=1.97)
pgsql-server/src/backend/rewrite:
rewriteManip.c (r1.84 -> r1.85)
(http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/backend/rewrite/rewriteManip.c.diff?r1=1.84&r2=1.85)
pgsql-server/src/backend/utils/adt:
ruleutils.c (r1.176 -> r1.177)
(http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/backend/utils/adt/ruleutils.c.diff?r1=1.176&r2=1.177)
pgsql-server/src/include/nodes:
primnodes.h (r1.100 -> r1.101)
(http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/include/nodes/primnodes.h.diff?r1=1.100&r2=1.101)
pgsql-server/src/include/parser:
parsetree.h (r1.24 -> r1.25)
(http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/include/parser/parsetree.h.diff?r1=1.24&r2=1.25)