Make Task and TaskWindowPrivate classes

They both used to be structs.

src/plugins/projectexplorer/task.h

@@ -39,7 +39,9 @@
 namespace ProjectExplorer {
 
 // Build issue (warning or error).
-struct PROJECTEXPLORER_EXPORT Task {
+class PROJECTEXPLORER_EXPORT Task
+{
+public:
     enum TaskType {
         Unknown,
         Error,

src/plugins/projectexplorer/taskwindow.cpp

@@ -478,7 +478,9 @@ bool TaskFilterModel::filterAcceptsRow(int sourceRow, const QModelIndex &sourceP
 // TaskWindow
 /////
 
-struct TaskWindowPrivate {
+class TaskWindowPrivate
+{
+public:
     Internal::TaskModel *m_model;
     Internal::TaskFilterModel *m_filter;
     Internal::TaskView *m_listview;

src/plugins/projectexplorer/taskwindow.h

@@ -42,10 +42,8 @@ class QModelIndex;
 QT_END_NAMESPACE
 
 namespace ProjectExplorer {
-struct Task;
-struct TaskWindowPrivate;
-
-struct TaskWindowPrivate;
+class Task;
+class TaskWindowPrivate;
 
 // Show build issues (warnings or errors) and open the editor on click.
 class PROJECTEXPLORER_EXPORT TaskWindow : public Core::IOutputPane