pgsql: Install some slightly realistic cost estimation for bitmap index

Log Message:
-----------
Install some slightly realistic cost estimation for bitmap index scans.

Modified Files:
--------------
    pgsql/src/backend/nodes:
        outfuncs.c (r1.247 -> r1.248)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/nodes/outfuncs.c.diff?r1=1.247&r2=1.248)
    pgsql/src/backend/optimizer/path:
        costsize.c (r1.142 -> r1.143)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/optimizer/path/costsize.c.diff?r1=1.142&r2=1.143)
        indxpath.c (r1.174 -> r1.175)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/optimizer/path/indxpath.c.diff?r1=1.174&r2=1.175)
        orindxpath.c (r1.67 -> r1.68)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/optimizer/path/orindxpath.c.diff?r1=1.67&r2=1.68)
    pgsql/src/backend/optimizer/plan:
        createplan.c (r1.180 -> r1.181)

(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/optimizer/plan/createplan.c.diff?r1=1.180&r2=1.181)
    pgsql/src/backend/optimizer/util:
        pathnode.c (r1.116 -> r1.117)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/optimizer/util/pathnode.c.diff?r1=1.116&r2=1.117)
    pgsql/src/include/nodes:
        relation.h (r1.105 -> r1.106)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/nodes/relation.h.diff?r1=1.105&r2=1.106)
    pgsql/src/include/optimizer:
        cost.h (r1.64 -> r1.65)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/optimizer/cost.h.diff?r1=1.64&r2=1.65)