pgsql: Support "variadic" functions, which can accept a variable number

Log Message:
-----------
Support "variadic" functions, which can accept a variable number of arguments
so long as all the trailing arguments are of the same (non-array) type.
The function receives them as a single array argument (which is why they
have to all be the same type).

It might be useful to extend this facility to aggregates, but this patch
doesn't do that.

This patch imposes a noticeable slowdown on function lookup --- a follow-on
patch will fix that by adding a redundant column to pg_proc.

Pavel Stehule

Modified Files:
--------------
    pgsql/doc/src/sgml:
        catalogs.sgml (r2.168 -> r2.169)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/catalogs.sgml?r1=2.168&r2=2.169)
        extend.sgml (r1.36 -> r1.37)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/extend.sgml?r1=1.36&r2=1.37)
        plpgsql.sgml (r1.131 -> r1.132)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/plpgsql.sgml?r1=1.131&r2=1.132)
        typeconv.sgml (r1.54 -> r1.55)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/typeconv.sgml?r1=1.54&r2=1.55)
        xfunc.sgml (r1.130 -> r1.131)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/xfunc.sgml?r1=1.130&r2=1.131)
    pgsql/doc/src/sgml/ref:
        alter_function.sgml (r1.15 -> r1.16)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/ref/alter_function.sgml?r1=1.15&r2=1.16)
        comment.sgml (r1.36 -> r1.37)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/ref/comment.sgml?r1=1.36&r2=1.37)
        create_function.sgml (r1.78 -> r1.79)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/ref/create_function.sgml?r1=1.78&r2=1.79)
        drop_function.sgml (r1.33 -> r1.34)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/ref/drop_function.sgml?r1=1.33&r2=1.34)
    pgsql/src/backend/catalog:
        information_schema.sql (r1.43 -> r1.44)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/catalog/information_schema.sql?r1=1.43&r2=1.44)
        namespace.c (r1.107 -> r1.108)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/catalog/namespace.c?r1=1.107&r2=1.108)
        pg_aggregate.c (r1.93 -> r1.94)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/catalog/pg_aggregate.c?r1=1.93&r2=1.94)
    pgsql/src/backend/commands:
        functioncmds.c (r1.95 -> r1.96)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/functioncmds.c?r1=1.95&r2=1.96)
    pgsql/src/backend/nodes:
        copyfuncs.c (r1.394 -> r1.395)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/nodes/copyfuncs.c?r1=1.394&r2=1.395)
        equalfuncs.c (r1.323 -> r1.324)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/nodes/equalfuncs.c?r1=1.323&r2=1.324)
        outfuncs.c (r1.326 -> r1.327)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/nodes/outfuncs.c?r1=1.326&r2=1.327)
    pgsql/src/backend/parser:
        gram.y (r2.616 -> r2.617)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/parser/gram.y?r1=2.616&r2=2.617)
        keywords.c (r1.198 -> r1.199)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/parser/keywords.c?r1=1.198&r2=1.199)
        parse_expr.c (r1.228 -> r1.229)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/parser/parse_expr.c?r1=1.228&r2=1.229)
        parse_func.c (r1.202 -> r1.203)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/parser/parse_func.c?r1=1.202&r2=1.203)
        parse_utilcmd.c (r2.13 -> r2.14)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/parser/parse_utilcmd.c?r1=2.13&r2=2.14)
    pgsql/src/backend/utils/adt:
        regproc.c (r1.107 -> r1.108)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/adt/regproc.c?r1=1.107&r2=1.108)
        ruleutils.c (r1.275 -> r1.276)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/adt/ruleutils.c?r1=1.275&r2=1.276)
    pgsql/src/backend/utils/fmgr:
        funcapi.c (r1.39 -> r1.40)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/fmgr/funcapi.c?r1=1.39&r2=1.40)
    pgsql/src/bin/pg_dump:
        pg_dump.c (r1.493 -> r1.494)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/bin/pg_dump/pg_dump.c?r1=1.493&r2=1.494)
    pgsql/src/bin/psql:
        describe.c (r1.181 -> r1.182)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/bin/psql/describe.c?r1=1.181&r2=1.182)
    pgsql/src/include/catalog:
        catversion.h (r1.468 -> r1.469)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/catversion.h?r1=1.468&r2=1.469)
        namespace.h (r1.54 -> r1.55)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/namespace.h?r1=1.54&r2=1.55)
        pg_proc.h (r1.506 -> r1.507)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/pg_proc.h?r1=1.506&r2=1.507)
    pgsql/src/include/nodes:
        parsenodes.h (r1.366 -> r1.367)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/nodes/parsenodes.h?r1=1.366&r2=1.367)
    pgsql/src/include/parser:
        parse_func.h (r1.59 -> r1.60)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/parser/parse_func.h?r1=1.59&r2=1.60)
    pgsql/src/interfaces/ecpg/preproc:
        preproc.y (r1.368 -> r1.369)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/ecpg/preproc/preproc.y?r1=1.368&r2=1.369)
    pgsql/src/pl/plpgsql/src:
        pl_comp.c (r1.126 -> r1.127)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/pl/plpgsql/src/pl_comp.c?r1=1.126&r2=1.127)
    pgsql/src/pl/plpython:
        plpython.c (r1.110 -> r1.111)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/pl/plpython/plpython.c?r1=1.110&r2=1.111)
    pgsql/src/test/regress/expected:
        plpgsql.out (r1.64 -> r1.65)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/expected/plpgsql.out?r1=1.64&r2=1.65)
        polymorphism.out (r1.12 -> r1.13)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/expected/polymorphism.out?r1=1.12&r2=1.13)
    pgsql/src/test/regress/sql:
        plpgsql.sql (r1.54 -> r1.55)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/sql/plpgsql.sql?r1=1.54&r2=1.55)
        polymorphism.sql (r1.5 -> r1.6)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/sql/polymorphism.sql?r1=1.5&r2=1.6)