news/pan: unbreak build with Clang 6 (C++14 by default)

text-match.cc:476:8: error: no viable conversion from 'pan::StringView' to 'std::__1::basic_string<char>'

s = tmp;
    ^~~

article-filter.cc:165:46: error: invalid suffix on literal; C++11 requires a space between literal

and identifier [-Wreserved-user-defined-literal]
      g_snprintf (buf, sizeof(buf), "%"G_GUINT64_FORMAT, xit->number);
                                       ^

Reported by: antoine (via bug 224669)