Port from QStringViewLiteral to u""

Now that all our supported compilers know char16_t, we no longer need
QStringViewLiteral, whose only purpose in life was to turn u"" into
L"" for MSVC < 2015.

Change-Id: I1f5f1cb31c8e8278189f7634850b209b46127ce5
Reviewed-by: Oliver Wolff <oliver.wolff@qt.io>

src/activeqt/control/qaxserverdll.cpp

@@ -88,7 +88,7 @@ STDAPI DllUnregisterServer()
 STDAPI DllInstall(BOOL bInstall, LPCWSTR pszCmdLine) {
     bool perUser = false; // per-user (un)registration
     if (pszCmdLine) {
-        if (QStringView(pszCmdLine).compare(QStringViewLiteral("user"), Qt::CaseInsensitive) == 0)
+        if (QStringView(pszCmdLine).compare(u"user", Qt::CaseInsensitive) == 0)
             perUser = true;
     }