pgsql: Move ltree parentsel() selectivity function into /contrib/ltree.

Log Message:
-----------
Move ltree parentsel() selectivity function into /contrib/ltree.

Modified Files:
--------------
    pgsql/contrib/ltree:
        ltree.sql.in (r1.11 -> r1.12)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/ltree/ltree.sql.in.diff?r1=1.11&r2=1.12)
        ltree_op.c (r1.9 -> r1.10)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/ltree/ltree_op.c.diff?r1=1.9&r2=1.10)
    pgsql/contrib/ltree/expected:
        ltree.out (r1.12 -> r1.13)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/ltree/expected/ltree.out.diff?r1=1.12&r2=1.13)
    pgsql/src/backend/utils/adt:
        geo_selfuncs.c (r1.28 -> r1.29)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/adt/geo_selfuncs.c.diff?r1=1.28&r2=1.29)
        selfuncs.c (r1.200 -> r1.201)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/adt/selfuncs.c.diff?r1=1.200&r2=1.201)
    pgsql/src/include/catalog:
        catversion.h (r1.325 -> r1.326)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/catversion.h.diff?r1=1.325&r2=1.326)
        pg_proc.h (r1.407 -> r1.408)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/pg_proc.h.diff?r1=1.407&r2=1.408)
    pgsql/src/include/utils:
        selfuncs.h (r1.29 -> r1.30)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/utils/selfuncs.h.diff?r1=1.29&r2=1.30)