Use LowestPriority instead of IdlePriority.

src/plugins/cppeditor/cppchecksymbols.h

@@ -62,7 +62,7 @@ public:
         this->setRunnable(this);
         this->reportStarted();
         Future future = this->future();
-        QThreadPool::globalInstance()->start(this, QThread::IdlePriority);
+        QThreadPool::globalInstance()->start(this, QThread::LowestPriority);
         return future;
     }
 

src/plugins/cppeditor/cppeditor.cpp

@@ -2041,7 +2041,7 @@ bool SemanticHighlighter::isOutdated()
 
 void SemanticHighlighter::run()
 {
-    setPriority(QThread::IdlePriority);
+    setPriority(QThread::LowestPriority);
 
     forever {
         m_mutex.lock();

src/plugins/qmljseditor/qmljseditor.cpp

@@ -1802,7 +1802,7 @@ bool SemanticHighlighter::isOutdated()
 
 void SemanticHighlighter::run()
 {
-    setPriority(QThread::IdlePriority);
+    setPriority(QThread::LowestPriority);
 
     forever {
         m_mutex.lock();