pgsql: ltree support for multibyte encodings.

Log Message:
-----------
ltree support for multibyte encodings. Patch was made by
laser <laserlist@pgsqldb.com> with some editorization by me.

Modified Files:
--------------
    pgsql/contrib/ltree:
        lquery_op.c (r1.12 -> r1.13)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/contrib/ltree/lquery_op.c?r1=1.12&r2=1.13)
        ltree.h (r1.20 -> r1.21)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/contrib/ltree/ltree.h?r1=1.20&r2=1.21)
        ltree_io.c (r1.16 -> r1.17)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/contrib/ltree/ltree_io.c?r1=1.16&r2=1.17)
        ltxtquery_io.c (r1.15 -> r1.16)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/contrib/ltree/ltxtquery_io.c?r1=1.15&r2=1.16)
        ltxtquery_op.c (r1.8 -> r1.9)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/contrib/ltree/ltxtquery_op.c?r1=1.8&r2=1.9)