C++: split defines into project-defined and toolchain-defined.

So we can ignore possibly problematic toolchain-defines, while can still
unconditionally apply project-defines.

Change-Id: I7cb96f35a963d080011fe888ef71bfc098dd33ef
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@digia.com>

src/plugins/cpptools/cppmodelmanagerinterface.h

@@ -106,7 +106,8 @@ public:
     QString projectFile;
     ProjectExplorer::Project *project;
     QList<ProjectFile> files;
-    QByteArray defines;
+    QByteArray projectDefines;
+    QByteArray toolchainDefines;
     QStringList includePaths;
     QStringList frameworkPaths;
     QStringList precompiledHeaders;