int remove_call_out(string fun)
int remove_call_out(closure fun)
Remove next pending call-out for function <fun> in the current
object, resp. the next pending call-out for closure <fun>.
The time left is returned.
-1 is returned if there were no call-outs pending to this
To remove every pending call-out to MyTimer() :
while (remove_call_out("MyTimer") != -1) /* continue */ ;
Removing a call_out to a closure was introduced in 3.2.1@45.
call_out(E), call_out_info(E), find_call_out(E)