bug#23826: 25.1.50; Wrong fontification of parameter in c++-mode

[Ivan Andrus]

>From `emacs -Q`, open a buffer in c++-mode and insert the following:

// X is fontified with font-lock-variable-face and x is not fontified
int foo(xml::XmlElement xml, X const& x )
{
    return 0;
}

// Fontified correctly
int bar(XmlElement xml, X const& x )
{
    return 1;
}


Notice that the namespace qualification of XmlElement causes the second
parameter to be incorrectly fontified (or so it appears).

-Ivan