pgsql: Code review for XML patch.

Log Message:
-----------
Code review for XML patch. Instill a bit of sanity in the location of
the XmlExpr code in various lists, use a representation that has some hope
of reverse-listing correctly (though it's still a de-escaping function
shy of correctness), generally try to make it look more like Postgres
coding conventions.

Modified Files:
--------------
pgsql/doc/src/sgml:
errcodes.sgml (r1.20 -> r1.21)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/errcodes.sgml.diff?r1=1.20&r2=1.21)
installation.sgml (r1.269 -> r1.270)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/installation.sgml.diff?r1=1.269&r2=1.270)
pgsql/src/backend/executor:
execQual.c (r1.201 -> r1.202)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/executor/execQual.c.diff?r1=1.201&r2=1.202)
pgsql/src/backend/nodes:
copyfuncs.c (r1.356 -> r1.357)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/nodes/copyfuncs.c.diff?r1=1.356&r2=1.357)
equalfuncs.c (r1.290 -> r1.291)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/nodes/equalfuncs.c.diff?r1=1.290&r2=1.291)
outfuncs.c (r1.288 -> r1.289)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/nodes/outfuncs.c.diff?r1=1.288&r2=1.289)
readfuncs.c (r1.198 -> r1.199)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/nodes/readfuncs.c.diff?r1=1.198&r2=1.199)
pgsql/src/backend/optimizer/util:
clauses.c (r1.225 -> r1.226)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/optimizer/util/clauses.c.diff?r1=1.225&r2=1.226)
pgsql/src/backend/parser:
gram.y (r2.569 -> r2.570)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/parser/gram.y.diff?r1=2.569&r2=2.570)
keywords.c (r1.178 -> r1.179)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/parser/keywords.c.diff?r1=1.178&r2=1.179)
parse_clause.c (r1.159 -> r1.160)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/parser/parse_clause.c.diff?r1=1.159&r2=1.160)
parse_coerce.c (r2.148 -> r2.149)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/parser/parse_coerce.c.diff?r1=2.148&r2=2.149)
parse_expr.c (r1.201 -> r1.202)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/parser/parse_expr.c.diff?r1=1.201&r2=1.202)
parse_target.c (r1.150 -> r1.151)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/parser/parse_target.c.diff?r1=1.150&r2=1.151)
pgsql/src/backend/utils/adt:
ruleutils.c (r1.237 -> r1.238)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/adt/ruleutils.c.diff?r1=1.237&r2=1.238)
xml.c (r1.2 -> r1.3)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/adt/xml.c.diff?r1=1.2&r2=1.3)
pgsql/src/include/catalog:
catversion.h (r1.365 -> r1.366)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/catversion.h.diff?r1=1.365&r2=1.366)
pg_proc.h (r1.431 -> r1.432)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/pg_proc.h.diff?r1=1.431&r2=1.432)
pgsql/src/include/nodes:
execnodes.h (r1.163 -> r1.164)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/nodes/execnodes.h.diff?r1=1.163&r2=1.164)
nodes.h (r1.189 -> r1.190)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/nodes/nodes.h.diff?r1=1.189&r2=1.190)
primnodes.h (r1.120 -> r1.121)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/nodes/primnodes.h.diff?r1=1.120&r2=1.121)
pgsql/src/include/parser:
parse_coerce.h (r1.67 -> r1.68)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/parser/parse_coerce.h.diff?r1=1.67&r2=1.68)
pgsql/src/include/utils:
xml.h (r1.2 -> r1.3)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/utils/xml.h.diff?r1=1.2&r2=1.3)
pgsql/src/pl/plpgsql/src:
pl_exec.c (r1.180 -> r1.181)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/pl/plpgsql/src/pl_exec.c.diff?r1=1.180&r2=1.181)
plerrcodes.h (r1.9 -> r1.10)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/pl/plpgsql/src/plerrcodes.h.diff?r1=1.9&r2=1.10)
pgsql/src/test/regress/expected:
opr_sanity.out (r1.70 -> r1.71)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/expected/opr_sanity.out.diff?r1=1.70&r2=1.71)
pgsql/src/test/regress/sql:
opr_sanity.sql (r1.56 -> r1.57)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/sql/opr_sanity.sql.diff?r1=1.56&r2=1.57)