$w->cb(undef) causes segfaults. (+patch)

(Does this mailing list exist?  My mail to [email protected] and
[email protected] doesn't return.  Perhaps mail on perl.org
is just slow.)

The following program segfaults after one second (when the watcher
triggers):

  use Event;
  my $w = Event->timer(after => 1, cb => sub {});
  $w->cb(undef);
  Event::loop;

The problem is that watchers are not stopped when their callback is
removed.  I am attaching a patch which appears to fix the problem.

                       - Damien

*** Event-0.81-orig/c/watcher.c	Tue Jun 13 08:24:24 2000
--- Event-0.81/c/watcher.c	Wed May 30 10:22:59 2001
***************
*** 90,95 ****
--- 90,96 ----
  	    WaPERLCB_off(ev);
  	    ev->callback = 0;
  	    ev->ext_data = 0;
+ 	    pe_watcher_stop(ev, 0);
  	} else if (SvROK(nval) && (SvTYPE(sv=SvRV(nval)) == SVt_PVCV)) {
  	    WaPERLCB_on(ev);
  	    ev->callback = SvREFCNT_inc(nval);