CppEditor:follow symbol:cursor is at the end of virtual function name

If the cursor is at the end of the virtual function name but before '('
then scope is a function.

Task-number: QTCREATORBUG-10294

Change-Id: I83699d3fa33bc0f33d6524fa6d84cfc2b9e71f85
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@digia.com>