pgsql: Rework join-removal logic as per recent discussion.

Log Message:
-----------
Rework join-removal logic as per recent discussion.  In particular this
fixes things so that it works for cases where nested removals are possible.
The overhead of the optimization should be significantly less, as well.

Modified Files:
--------------
    pgsql/src/backend/nodes:
        outfuncs.c (r1.383 -> r1.384)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/nodes/outfuncs.c?r1=1.383&r2=1.384)
    pgsql/src/backend/optimizer:
        README (r1.52 -> r1.53)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/optimizer/README?r1=1.52&r2=1.53)
    pgsql/src/backend/optimizer/path:
        allpaths.c (r1.193 -> r1.194)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/optimizer/path/allpaths.c?r1=1.193&r2=1.194)
        joinpath.c (r1.131 -> r1.132)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/optimizer/path/joinpath.c?r1=1.131&r2=1.132)
    pgsql/src/backend/optimizer/plan:
        Makefile (r1.15 -> r1.16)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/optimizer/plan/Makefile?r1=1.15&r2=1.16)
        createplan.c (r1.273 -> r1.274)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/optimizer/plan/createplan.c?r1=1.273&r2=1.274)
        planmain.c (r1.117 -> r1.118)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/optimizer/plan/planmain.c?r1=1.117&r2=1.118)
    pgsql/src/backend/optimizer/util:
        pathnode.c (r1.157 -> r1.158)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/optimizer/util/pathnode.c?r1=1.157&r2=1.158)
        placeholder.c (r1.6 -> r1.7)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/optimizer/util/placeholder.c?r1=1.6&r2=1.7)
    pgsql/src/include/nodes:
        nodes.h (r1.233 -> r1.234)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/nodes/nodes.h?r1=1.233&r2=1.234)
        relation.h (r1.184 -> r1.185)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/nodes/relation.h?r1=1.184&r2=1.185)
    pgsql/src/include/optimizer:
        pathnode.h (r1.83 -> r1.84)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/optimizer/pathnode.h?r1=1.83&r2=1.84)
        placeholder.h (r1.4 -> r1.5)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/optimizer/placeholder.h?r1=1.4&r2=1.5)
        planmain.h (r1.126 -> r1.127)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/optimizer/planmain.h?r1=1.126&r2=1.127)
    pgsql/src/test/regress/expected:
        join.out (r1.44 -> r1.45)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/expected/join.out?r1=1.44&r2=1.45)
    pgsql/src/test/regress/sql:
        join.sql (r1.33 -> r1.34)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/sql/join.sql?r1=1.33&r2=1.34)

Added Files:
-----------
    pgsql/src/backend/optimizer/plan:
        analyzejoins.c (r1.1)

(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/optimizer/plan/analyzejoins.c?rev=1.1&content-type=text/x-cvsweb-markup)