Append the Windows OS/kernel version number in QSysInfo::prettyProductName().

The rationale is to be consistent with other operating systems, all of which
print a version number following their name (possibly in parenthesis if the
version is typically non-numeric as is always the case with OS X so far and
has been with Windows).

The version number printed here is only two digits, both for consistency with
OS X and because the first two digits of an operating systems's version are
typically the limit in marketing materials and general presentation.

This also fixes a bug where the returned string would be "Windows " (note the
space) in the case where the name of a future Windows version was not known.

[ChangeLog][QtCore][QSysInfo] The output of QSysInfo::prettyProductName
now includes the Windows OS/kernel version number. In case of future versions
of Windows, a valid string is now returned.

Change-Id: I588c2e0aaae19337eb69b4645f8bccf8270c75bc
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/corelib/global/qglobal.cpp

@@ -2782,7 +2782,17 @@ QString QSysInfo::prettyProductName()
 #elif defined(Q_OS_WINPHONE)
     return QLatin1String("Windows Phone ") + QLatin1String(winVer_helper());
 #elif defined(Q_OS_WIN)
-    return QLatin1String("Windows ") + QLatin1String(winVer_helper()) + winSp_helper();
+    const char *name = winVer_helper();
+    const OSVERSIONINFOEX osver = winOsVersion();
+    if (name)
+        return QLatin1String("Windows ") + QLatin1String(name) + winSp_helper()
+            + QLatin1String(" (") + QString::number(osver.dwMajorVersion)
+            + QLatin1Char('.') + QString::number(osver.dwMinorVersion)
+            + QLatin1Char(')');
+    else
+        return QLatin1String("Windows ")
+            + QString::number(osver.dwMajorVersion) + QLatin1Char('.')
+            + QString::number(osver.dwMinorVersion);
 #elif defined(Q_OS_ANDROID)
     return QLatin1String("Android ") + productVersion();
 #elif defined(Q_OS_HAIKU)