- Fixed bug in :func:`.tuple_` construct where the "type" of essentially

- Fixed bug in :func:`.tuple_` construct where the "type" of essentially
the first SQL expression would be applied as the "comparison type"
to a compared tuple value; this has the effect in some cases of an
inappropriate "type coersion" occurring, such as when a tuple that
has a mix of String and Binary values improperly coerces target
values to Binary even though that's not what they are on the left
side.  :func:`.tuple_` now expects heterogeneous types within its
list of values.
fixes #2977

Conflicts:
	lib/sqlalchemy/sql/elements.py
	test/sql/test_operators.py