pgsql: Previous fix for "x FULL JOIN y ON true" failed to handle the

Log Message:
-----------
Previous fix for "x FULL JOIN y ON true" failed to handle the case
where there was also a WHERE-clause restriction that applied to the
join.  The check on restrictlist == NIL is really unnecessary anyway,
because select_mergejoin_clauses already checked for and complained
about any unmergejoinable join clauses.  So just take it out.

Modified Files:
--------------
    pgsql/src/backend/optimizer/path:
        joinpath.c (r1.93 -> r1.94)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/optimizer/path/joinpath.c.diff?r1=1.93&r2=1.94)