Add a menu option to verify a signed message

(Also move 'setAttribute(Qt::WA_DeleteOnClose)' out of QRCodeDialog)

src/qt/verifymessagedialog.h

@@ -0,0 +1,36 @@
+#ifndef VERIFYMESSAGEDIALOG_H
+#define VERIFYMESSAGEDIALOG_H
+
+#include <QDialog>
+
+class AddressTableModel;
+
+QT_BEGIN_NAMESPACE
+class QAbstractButton;
+QT_END_NAMESPACE
+
+namespace Ui {
+    class VerifyMessageDialog;
+}
+
+class VerifyMessageDialog : public QDialog
+{
+    Q_OBJECT
+
+public:
+    explicit VerifyMessageDialog(AddressTableModel *addressModel, QWidget *parent = 0);
+    ~VerifyMessageDialog();
+
+private slots:
+    void on_buttonBox_clicked(QAbstractButton *button);
+
+    void on_copyToClipboard_clicked();
+
+private:
+    bool checkAddress();
+
+    Ui::VerifyMessageDialog *ui;
+    AddressTableModel *model;
+};
+
+#endif // VERIFYMESSAGEDIALOG_H