Give the values of BuildStep::OutputFormat better names

The old ones did not convey their meaning very well. In particular,
NormalOutput and MessageOutput were easily confused.

Change-Id: Ia0a8c1b1c366ab3f5c59f751b37b8b1f68f6831d
Reviewed-by: Tobias Hunger <tobias.hunger@qt.io>

src/plugins/qbsprojectmanager/qbscleanstep.cpp

@@ -200,7 +200,7 @@ void QbsCleanStep::createTaskAndOutput(ProjectExplorer::Task::TaskType type, con
                                                        Utils::FileName::fromString(file), line,
                                                        ProjectExplorer::Constants::TASK_CATEGORY_COMPILE);
     emit addTask(task, 1);
-    emit addOutput(message, NormalOutput);
+    emit addOutput(message, OutputFormat::Stdout);
 }
 
 void QbsCleanStep::setDryRun(bool dr)