pgsql: Fix rtree and contrib/rtree_gist search behavior for the 1-D box

Log Message:
-----------
Fix rtree and contrib/rtree_gist search behavior for the 1-D box and
polygon operators (<<, &<, >>, &>).  Per ideas originally put forward
by andrew@supernews and later rediscovered by moi.  This patch just
fixes the existing opclasses, and does not add any new behavior as I
proposed earlier; that can be sorted out later.  In principle this
could be back-patched, since it changes only search behavior and not
system catalog entries nor rtree index contents.  I'm not currently
planning to do that, though, since I think it could use more testing.

Modified Files:
--------------
    pgsql/contrib/rtree_gist:
        rtree_gist.c (r1.12 -> r1.13)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/rtree_gist/rtree_gist.c.diff?r1=1.12&r2=1.13)
    pgsql/src/backend/access/common:
        indexvalid.c (r1.33 -> r1.34)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/common/indexvalid.c.diff?r1=1.33&r2=1.34)
    pgsql/src/backend/access/rtree:
        rtscan.c (r1.58 -> r1.59)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/rtree/rtscan.c.diff?r1=1.58&r2=1.59)
        rtstrat.c (r1.25 -> r1.26)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/rtree/rtstrat.c.diff?r1=1.25&r2=1.26)
    pgsql/src/include/access:
        rtree.h (r1.39 -> r1.40)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/access/rtree.h.diff?r1=1.39&r2=1.40)
        skey.h (r1.28 -> r1.29)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/access/skey.h.diff?r1=1.28&r2=1.29)