C++ editor: Fix follow symbol for member functions

Fix a regression introduced by ad53fa42
in which follow symbol takes you to the function declaration (instead
of to the type) for situations like the one below (the | indicates the
cursor):

void Ty|pe::function() {}

Change-Id: Iffd15b23bb0cd67eca5965cb22d9b60c4d024fb7
Reviewed-on: http://codereview.qt.nokia.com/1375


Reviewed-by: Erik Verbruggen <erik.verbruggen@nokia.com>