update the explanation for deprecating v0 control spec.

svn:r6521

doc/control-spec-v0.txt

@@ -4,8 +4,9 @@ $Id$
 
 -1. Deprecation
 
-THIS PROTOCOL IS DEPRECATED.  It is still documented here because it is the
+THIS PROTOCOL IS DEPRECATED.  It is still documented here because Tor
-only Tor control protocol supported in the Tor implementation right now.
+0.1.1.x happens to support much of it; but the support for v0 is not
+maintained, so you should expect it to rot in unpredictable ways.
 
 0. Scope