Fix MSVC-warnings in CppEditor.

cppfollowsymbolundercursor.cpp(174) : warning C4100: 'widget' :
unreferenced parameter

cppvirtualfunctionassistprovider.cpp(61) : warning C4138: '*/' found
outside of comment

Change-Id: I9c14aff54b88daa6eda9a217db2fc314e9f07742
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@digia.com>