pgsql: Create executor and planner-backend support for decoupled heap

Log Message:
-----------
Create executor and planner-backend support for decoupled heap and index
scans, using in-memory tuple ID bitmaps as the intermediary.  The planner
frontend (path creation and cost estimation) is not there yet, so none
of this code can be executed.  I have tested it using some hacked planner
code that is far too ugly to see the light of day, however.  Committing
now so that the bulk of the infrastructure changes go in before the tree
drifts under me.

Modified Files:
--------------
    pgsql/src/backend/commands:
        explain.c (r1.132 -> r1.133)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/explain.c.diff?r1=1.132&r2=1.133)
    pgsql/src/backend/executor:
        Makefile (r1.22 -> r1.23)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/executor/Makefile.diff?r1=1.22&r2=1.23)
        execAmi.c (r1.82 -> r1.83)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/executor/execAmi.c.diff?r1=1.82&r2=1.83)
        execProcnode.c (r1.49 -> r1.50)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/executor/execProcnode.c.diff?r1=1.49&r2=1.50)
    pgsql/src/backend/nodes:
        copyfuncs.c (r1.301 -> r1.302)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/nodes/copyfuncs.c.diff?r1=1.301&r2=1.302)
        outfuncs.c (r1.246 -> r1.247)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/nodes/outfuncs.c.diff?r1=1.246&r2=1.247)
        print.c (r1.74 -> r1.75)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/nodes/print.c.diff?r1=1.74&r2=1.75)
        tidbitmap.c (r1.1 -> r1.2)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/nodes/tidbitmap.c.diff?r1=1.1&r2=1.2)
    pgsql/src/backend/optimizer/path:
        allpaths.c (r1.125 -> r1.126)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/optimizer/path/allpaths.c.diff?r1=1.125&r2=1.126)
        costsize.c (r1.141 -> r1.142)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/optimizer/path/costsize.c.diff?r1=1.141&r2=1.142)
        joinpath.c (r1.92 -> r1.93)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/optimizer/path/joinpath.c.diff?r1=1.92&r2=1.93)
    pgsql/src/backend/optimizer/plan:
        createplan.c (r1.179 -> r1.180)

(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/optimizer/plan/createplan.c.diff?r1=1.179&r2=1.180)
        setrefs.c (r1.106 -> r1.107)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/optimizer/plan/setrefs.c.diff?r1=1.106&r2=1.107)
        subselect.c (r1.96 -> r1.97)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/optimizer/plan/subselect.c.diff?r1=1.96&r2=1.97)
    pgsql/src/backend/optimizer/util:
        pathnode.c (r1.115 -> r1.116)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/optimizer/util/pathnode.c.diff?r1=1.115&r2=1.116)
    pgsql/src/include/executor:
        nodeIndexscan.h (r1.21 -> r1.22)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/executor/nodeIndexscan.h.diff?r1=1.21&r2=1.22)
    pgsql/src/include/nodes:
        execnodes.h (r1.125 -> r1.126)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/nodes/execnodes.h.diff?r1=1.125&r2=1.126)
        nodes.h (r1.166 -> r1.167)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/nodes/nodes.h.diff?r1=1.166&r2=1.167)
        plannodes.h (r1.77 -> r1.78)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/nodes/plannodes.h.diff?r1=1.77&r2=1.78)
        relation.h (r1.104 -> r1.105)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/nodes/relation.h.diff?r1=1.104&r2=1.105)
    pgsql/src/include/optimizer:
        cost.h (r1.63 -> r1.64)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/optimizer/cost.h.diff?r1=1.63&r2=1.64)
        pathnode.h (r1.57 -> r1.58)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/optimizer/pathnode.h.diff?r1=1.57&r2=1.58)

Added Files:
-----------
    pgsql/src/backend/executor:
        nodeBitmapAnd.c (r1.1)

(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/executor/nodeBitmapAnd.c?rev=1.1&content-type=text/x-cvsweb-markup)
        nodeBitmapHeapscan.c (r1.1)

(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/executor/nodeBitmapHeapscan.c?rev=1.1&content-type=text/x-cvsweb-markup)
        nodeBitmapIndexscan.c (r1.1)

(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/executor/nodeBitmapIndexscan.c?rev=1.1&content-type=text/x-cvsweb-markup)
        nodeBitmapOr.c (r1.1)

(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/executor/nodeBitmapOr.c?rev=1.1&content-type=text/x-cvsweb-markup)
    pgsql/src/include/executor:
        nodeBitmapAnd.h (r1.1)

(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/executor/nodeBitmapAnd.h?rev=1.1&content-type=text/x-cvsweb-markup)
        nodeBitmapHeapscan.h (r1.1)

(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/executor/nodeBitmapHeapscan.h?rev=1.1&content-type=text/x-cvsweb-markup)
        nodeBitmapIndexscan.h (r1.1)

(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/executor/nodeBitmapIndexscan.h?rev=1.1&content-type=text/x-cvsweb-markup)
        nodeBitmapOr.h (r1.1)

(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/executor/nodeBitmapOr.h?rev=1.1&content-type=text/x-cvsweb-markup)