Editor: Allow creating block selections with alt+shift again

These block selections are a convenience for people used to the block
selection allowing to also unselect parts again (at least as long as
alt+shift is pressed).

Fixes: QTCREATORBUG-26535
Fixes: QTCREATORBUG-26529
Change-Id: I19558dc1d823c268cc1cfda0ea8151bac483701f
Reviewed-by: Orgad Shaneh <orgads@gmail.com>

src/libs/utils/multitextcursor.h

@@ -27,6 +27,7 @@
 
 #include "utils_global.h"
 
+#include <QKeySequence>
 #include <QTextCursor>
 
 QT_BEGIN_NAMESPACE
@@ -99,6 +100,8 @@ public:
     const_iterator constBegin() const { return m_cursors.constBegin(); }
     const_iterator constEnd() const { return m_cursors.constEnd(); }
 
+    static bool multiCursorAddEvent(QKeyEvent *e, QKeySequence::StandardKey matchKey);
+
 private:
     QList<QTextCursor> m_cursors;
 };