Fix for lack of "use" statement in BaseQuery subclasses in single table inheritance when using namespaces

Requiements:
* we are using namespace for all classes generated by Propel
* we have Book class which has subclasses Essay & Comic

Problem:
* generated BaseEssayQuery class extends BookQuery but it does not have "use" statement for it so it causes errors

Solution:
* call class declaration when parent class name is being guessed (it adds required use statement if it wasn't already defined)