Filter by entity with NOT_EQUAL fails with composite key

[benbankes]

This is just documentation for myself since Propel1 is not being actively supported.

When filtering by a foreign entity, and using Criteria::NOT_EQUAL, the resulting query contains:
... AND entity.a <> 'valuea' AND entity.b <> 'valueb' ...
where instead it should have
... AND NOT(entity.a = 'valuea' AND entity.b = 'valueb') ...

[benbankes]

Found in 1.6.7