Add missing documentation for QOperatingSystemVersion::segmentCount

Change-Id: I6d24fbbaf60e07377a463ea1f72588812caaf4a7
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/corelib/global/qoperatingsystemversion.cpp

@@ -281,6 +281,12 @@ int QOperatingSystemVersion::compare(const QOperatingSystemVersion &v1,
     \sa majorVersion(), minorVersion()
 */
 
+/*!
+    \fn int QOperatingSystemVersion::segmentCount() const
+
+    Returns the number of integers stored in the version number.
+*/
+
 /*!
     \fn QOperatingSystemVersion::OSType QOperatingSystemVersion::type() const