C++: wrong tooltip behind function without args

Example code:
float fun()
{
    return 0;
}

Hovering in the area behind the function without args(but in the same line,
in above example after "float fun()") will bring up tooltip with returned
value of this function(in the above example it will be "float").

Fixed by checking this special case after gathering results for tooltip
and don't show confusing tooltip.

Task-number: QTCREATORBUG-4780
Change-Id: Iab2bacddf33a70d5ea941001a2dd317c824d9db5
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@digia.com>