CppEditor: "Follow Symbol Under Cursor" for virtual functions

F2 on a virtual function call presents a list of overrides in derived
classes. The function declaration of the static type is shown
immediately at the top.

Task-number: QTCREATORBUG-9611

Change-Id: I80ce906fa06272dc9fbd1662cd17500b8c77067f
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>

src/plugins/texteditor/codeassist/genericproposalwidget.h

@@ -32,11 +32,13 @@
 
 #include "iassistproposalwidget.h"
 
+#include <texteditor/texteditor_global.h>
+
 namespace TextEditor {
 
 class GenericProposalWidgetPrivate;
 
-class GenericProposalWidget : public IAssistProposalWidget
+class TEXTEDITOR_EXPORT GenericProposalWidget : public IAssistProposalWidget
 {
     Q_OBJECT
     friend class GenericProposalWidgetPrivate;
@@ -69,6 +71,7 @@ private slots:
 
 protected:
     virtual bool eventFilter(QObject *o, QEvent *e);
+    bool activateCurrentProposalItem();
 
 private:
     GenericProposalWidgetPrivate *d;