debugger: create a disassembler view as main editor

"Stepping instruction wise" and "display disassembler" mode is now toggled by a
single action. This also allows to re-use F10 and F11 as keyboard shortcut.

Missing: caching of disassembler output, removal of old disassembler view.

src/plugins/debugger/registerhandler.cpp

@@ -76,6 +76,12 @@ QVariant RegisterHandler::data(const QModelIndex &index, int role) const
 
     const Register &reg = m_registers.at(index.row());
 
+    if (role == Qt::UserRole + 1) {
+        bool ok = true;
+        qulonglong value = reg.value.toULongLong(&ok, 0);
+        return QString::fromLatin1("0x") + QString::number(value, 16);
+    }
+
     const QString padding = "  ";
     if (role == Qt::DisplayRole) {
         switch (index.column()) {