Clang: Move unexported classes to Internal

Change-Id: I3ea197b734f146d4b11431aaf927aed9be7d8756
Reviewed-by: Orgad Shaneh <orgads@gmail.com>
Reviewed-by: Ivan Donchevskii <ivan.donchevskii@qt.io>

src/plugins/clangcodemodel/clangeditordocumentparser.h

@@ -28,6 +28,7 @@
 #include <cpptools/baseeditordocumentparser.h>
 
 namespace ClangCodeModel {
+namespace Internal {
 
 class ClangEditorDocumentParser : public CppTools::BaseEditorDocumentParser
 {
@@ -41,4 +42,5 @@ private:
                     const UpdateParams &updateParams) override;
 };
 
+} // namespace Internal
 } // namespace ClangCodeModel