logic: Use all available cores when setting indexer threads to 0 (issue #342)

src/lib_gui/utility/utilityApp.cpp

@@ -1,6 +1,7 @@
 #include "utility/utilityApp.h"
 
 #include <QProcess>
+#include <QThread>
 #include <qprocessordetection.h>
 
 #include "utility/utilityString.h"
@@ -35,3 +36,8 @@ ApplicationArchitectureType utility::getApplicationArchitectureType()
 #endif
 	return APPLICATION_ARCHITECTURE_UNKNOWN;
 }
+
+int utility::getIdealThreadCount()
+{
+	return QThread::idealThreadCount();
+}