CppEditor: Use the project part chosen with CppPreProcessorDialog

...otherwise the CppPreProcessorDialog is only semi-useful.

Change-Id: I6b80967b05e7c9a51cd78ae064a3d78170948e32
Reviewed-by: David Schulz <david.schulz@digia.com>
Reviewed-by: Erik Verbruggen <erik.verbruggen@digia.com>
Reviewed-by: Eike Ziller <eike.ziller@digia.com>

src/plugins/cppeditor/cpppreprocessordialog.cpp

@@ -112,6 +112,11 @@ int CppPreProcessorDialog::exec()
     return Accepted;
 }
 
+CppTools::ProjectPart::Ptr CppPreProcessorDialog::projectPart() const
+{
+    return m_partAdditions[m_ui->projectComboBox->currentIndex()].projectPart;
+}
+
 QString CppPreProcessorDialog::additionalPreProcessorDirectives() const
 {
     return m_ui->editWidget->toPlainText();