C++ editor: Highlight member variable

Highlight member variable when there is also
enum value with the same name

Task-number: QTCREATORBUG-7525
Change-Id: I0990844a20fdf9e87a807fde10708344b9c3497b
Reviewed-by: Orgad Shaneh <orgads@gmail.com>
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@digia.com>