HHH-5654 PostgreSQL81Dialect will now correctly apply "for update of" for...

... any necessary table aliases. Added test.  PostgreSQL 8.1+ does support SELECT ... FOR UPDATE OF x,y,z
http://www.postgresql.org/docs/8.1/static/sql-select.html

Fix for this old issue can very likely be cherry-picked and applied to older release branches as well.

Signed-off-by: Bradley Plies <pliesb@yahoo.com>