Debugger: Improve configuration error reporting.

- Make showWarningWithOptions actually show the details.
- Show errors from multiple engines as separate messages.
- Remove 'enabled' option from CDB (handled by toolchain config now).
- Show ABI as tooltip in debbugger toolchain chooser.

src/plugins/coreplugin/mainwindow.cpp

@@ -1386,7 +1386,7 @@ bool MainWindow::showWarningWithOptions(const QString &title,
         parent = this;
     QMessageBox msgBox(QMessageBox::Warning, title, text,
                        QMessageBox::Ok, parent);
-    if (details.isEmpty())
+    if (!details.isEmpty())
         msgBox.setDetailedText(details);
     QAbstractButton *settingsButton = 0;
     if (!settingsId.isEmpty() || !settingsCategory.isEmpty())