error message delivery threading fixes

the message manager is not thread-safe, so don't use it outside the main
thread.

src/plugins/qt4projectmanager/qt4project.cpp

@@ -932,7 +932,8 @@ ProFileReader *Qt4Project::createProFileReader(Qt4ProFileNode *qt4ProFileNode)
 
     ProFileReader *reader = new ProFileReader(m_proFileOption);
     connect(reader, SIGNAL(errorFound(QString)),
-            this, SLOT(proFileParseError(QString)));
+            this, SLOT(proFileParseError(QString)),
+            Qt::QueuedConnection);
 
     reader->setOutputDir(qt4ProFileNode->buildDir());