pgsql: Code review for function default parameters patch.

Log Message:
-----------
Code review for function default parameters patch.  Fix numerous problems as
per recent discussions.  In passing this also fixes a couple of bugs in
the previous variadic-parameters patch.

Modified Files:
--------------
    pgsql/doc/src/sgml:
        catalogs.sgml (r2.183 -> r2.184)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/catalogs.sgml?r1=2.183&r2=2.184)
        func.sgml (r1.461 -> r1.462)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/func.sgml?r1=1.461&r2=1.462)
        typeconv.sgml (r1.57 -> r1.58)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/typeconv.sgml?r1=1.57&r2=1.58)
        xfunc.sgml (r1.135 -> r1.136)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/xfunc.sgml?r1=1.135&r2=1.136)
    pgsql/doc/src/sgml/ref:
        create_function.sgml (r1.82 -> r1.83)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/ref/create_function.sgml?r1=1.82&r2=1.83)
    pgsql/src/backend/catalog:
        namespace.c (r1.114 -> r1.115)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/catalog/namespace.c?r1=1.114&r2=1.115)
        pg_aggregate.c (r1.98 -> r1.99)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/catalog/pg_aggregate.c?r1=1.98&r2=1.99)
        pg_proc.c (r1.155 -> r1.156)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/catalog/pg_proc.c?r1=1.155&r2=1.156)
    pgsql/src/backend/commands:
        functioncmds.c (r1.102 -> r1.103)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/functioncmds.c?r1=1.102&r2=1.103)
        proclang.c (r1.81 -> r1.82)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/proclang.c?r1=1.81&r2=1.82)
    pgsql/src/backend/optimizer/plan:
        planner.c (r1.246 -> r1.247)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/optimizer/plan/planner.c?r1=1.246&r2=1.247)
    pgsql/src/backend/optimizer/util:
        clauses.c (r1.270 -> r1.271)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/optimizer/util/clauses.c?r1=1.270&r2=1.271)
    pgsql/src/backend/parser:
        gram.y (r2.644 -> r2.645)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/parser/gram.y?r1=2.644&r2=2.645)
        parse_func.c (r1.208 -> r1.209)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/parser/parse_func.c?r1=1.208&r2=1.209)
    pgsql/src/backend/utils/adt:
        regproc.c (r1.108 -> r1.109)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/adt/regproc.c?r1=1.108&r2=1.109)
        ruleutils.c (r1.288 -> r1.289)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/adt/ruleutils.c?r1=1.288&r2=1.289)
    pgsql/src/bin/pg_dump:
        pg_dump.c (r1.507 -> r1.508)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/bin/pg_dump/pg_dump.c?r1=1.507&r2=1.508)
    pgsql/src/include/catalog:
        namespace.h (r1.56 -> r1.57)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/namespace.h?r1=1.56&r2=1.57)
        pg_attribute.h (r1.142 -> r1.143)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/pg_attribute.h?r1=1.142&r2=1.143)
        pg_proc.h (r1.530 -> r1.531)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/pg_proc.h?r1=1.530&r2=1.531)
        pg_proc_fn.h (r1.3 -> r1.4)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/pg_proc_fn.h?r1=1.3&r2=1.4)
    pgsql/src/include/nodes:
        parsenodes.h (r1.382 -> r1.383)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/nodes/parsenodes.h?r1=1.382&r2=1.383)
    pgsql/src/include/parser:
        parse_func.h (r1.61 -> r1.62)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/parser/parse_func.h?r1=1.61&r2=1.62)
    pgsql/src/test/regress/expected:
        opr_sanity.out (r1.86 -> r1.87)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/expected/opr_sanity.out?r1=1.86&r2=1.87)
        polymorphism.out (r1.16 -> r1.17)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/expected/polymorphism.out?r1=1.16&r2=1.17)
    pgsql/src/test/regress/sql:
        opr_sanity.sql (r1.70 -> r1.71)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/sql/opr_sanity.sql?r1=1.70&r2=1.71)
        polymorphism.sql (r1.9 -> r1.10)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/sql/polymorphism.sql?r1=1.9&r2=1.10)