Merge pull request #1927 from YosysHQ/eddie/design_remove_assert

kernel: Design::remove(RTLIL::Module *) to check refcount_modules_

kernel/rtlil.cc

@@ -597,6 +597,7 @@ void RTLIL::Design::remove(RTLIL::Module *module)
 	}
 
 	log_assert(modules_.at(module->name) == module);
+	log_assert(refcount_modules_ == 0);
 	modules_.erase(module->name);
 	delete module;
 }