Fix exported headers in Core and TextEditor.

- Unexport Core::Internal::MainWindow and remove its includes.
- Move RssFetcher from Core::Internal to Core.
- Unexport CopyTaskHandler.
- Move TextEditor's completion support and Refactor Overlay
  helper classes from TextEditor::Internal to TextEditor as they
  are exported.
- Move internal BaseTextBlockSelection into private header.
- Unexport TextEditorOverlay as they are not used.

src/plugins/projectexplorer/miniprojecttargetselector.cpp

@@ -37,7 +37,6 @@
 #include <utils/stylehelper.h>
 
 #include <coreplugin/icore.h>
-#include <coreplugin/mainwindow.h>
 #include <coreplugin/coreconstants.h>
 
 #include <projectexplorer/projectexplorer.h>
@@ -57,6 +56,7 @@
 #include <QtGui/QPainter>
 #include <QtGui/QAction>
 #include <QtGui/QItemDelegate>
+#include <QtGui/QMainWindow>
 
 #include <QtGui/QApplication>