SVN: Document minimum required Subversion version

Change-Id: Ia689f7686b1efe30e839aa03a5a3f9c5cd801915
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@digia.com>

doc/src/howto/creator-vcs.qdoc

@@ -63,6 +63,7 @@
         \row
             \li Subversion
             \li \l{http://subversion.apache.org/}
+            \li Subversion version 1.6.17 and later
             \li
     \endtable