ProjectExplorer: Let IOutputParser handle newlines

This makes IOutputParser structurally more similar to
Utils::OutputFormatter, which makes it simpler to explore possibilities
of somehow uniting these two related classes.

Task-number: QTCREATORBUG-22665
Change-Id: Ibb12ab6c8c785d863b9a921102a929864d0a5251
Reviewed-by: hjk <hjk@qt.io>

src/plugins/cmakeprojectmanager/cmakeprocess.cpp

@@ -201,7 +201,7 @@ void CMakeProcess::processStandardError()
 
     static QString rest;
     rest = lineSplit(rest, m_process->readAllStandardError(), [this](const QString &s) {
-        m_parser->stdError(s);
+        m_parser->handleStderr(s);
         Core::MessageManager::write(s);
     });
 }