merge from tip

diff --cc lib/sqlalchemy/engine/base.py
Simple merge

diff --cc lib/sqlalchemy/orm/mapper.py
Simple merge

diff --cc lib/sqlalchemy/orm/state.py
Simple merge

diff --cc lib/sqlalchemy/orm/strategies.py
Simple merge

diff --cc lib/sqlalchemy/util.py
Simple merge

diff --cc test/engine/test_pool.py
Simple merge