pgsql: Minor performance improvement: avoid unnecessary

Log Message:
-----------
Minor performance improvement: avoid unnecessary creation/unioning of
bitmaps for multiple indexscans.  Instead just let each indexscan add
TIDs directly into the BitmapOr node's result bitmap.

Modified Files:
--------------
    pgsql/src/backend/executor:
        nodeBitmapAnd.c (r1.1 -> r1.2)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/executor/nodeBitmapAnd.c.diff?r1=1.1&r2=1.2)
        nodeBitmapIndexscan.c (r1.1 -> r1.2)

(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/executor/nodeBitmapIndexscan.c.diff?r1=1.1&r2=1.2)
        nodeBitmapOr.c (r1.1 -> r1.2)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/executor/nodeBitmapOr.c.diff?r1=1.1&r2=1.2)
    pgsql/src/include/nodes:
        execnodes.h (r1.126 -> r1.127)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/nodes/execnodes.h.diff?r1=1.126&r2=1.127)