analyzer: add logging of aliasing

gcc/analyzer/ChangeLog:
	* engine.cc (impl_run_checkers): Pass logger to engine ctor.
	* region-model-manager.cc
	(region_model_manager::region_model_manager): Add logger param and
	use it to initialize m_logger.
	* region-model.cc (engine::engine): New.
	* region-model.h (region_model_manager::region_model_manager):
	Add logger param.
	(region_model_manager::get_logger): New.
	(region_model_manager::m_logger): New field.
	(engine::engine): New.
	* store.cc (store_manager::get_logger): New.
	(store::set_value): Log scope.  Log when marking a cluster as
	unknown due to possible aliasing.
	* store.h (store_manager::get_logger): New decl.