docs: slots: auto: Mention why it is bad.

murraycu · murraycu · commit 49a05a0fdfcc · 2016-04-01T11:47:03.000+02:00
diff --git a/sigc++/functors/slot_base.h b/sigc++/functors/slot_base.h
@@ -213,6 +213,10 @@ struct SIGC_API slot_do_unbind
  * auto sl = sigc::mem_fun(someobj, &SomeClass::somemethod); // Not a slot!
  * @endcode
  *
+ * If you don't explicitly use a sigc::slot then the slot could call a method
+ * on an instance after it has been destroyed even if the method is in a class
+ * that derives from sigc::trackable.
+ *
  * @section slots-with-lambdas C++ Lambdas
  *
  * A C++11 lambda expression is a functor (function object). It is automatically

Original file line number	Diff line number	Diff line change
`@@ -213,6 +213,10 @@ struct SIGC_API slot_do_unbind`
`213`	`213`	`* auto sl = sigc::mem_fun(someobj, &SomeClass::somemethod); // Not a slot!`
`214`	`214`	`* @endcode`
`215`	`215`	`*`
	`216`	`+ * If you don't explicitly use a sigc::slot then the slot could call a method`
	`217`	`+ * on an instance after it has been destroyed even if the method is in a class`
	`218`	`+ * that derives from sigc::trackable.`
	`219`	`+ *`
`216`	`220`	`* @section slots-with-lambdas C++ Lambdas`
`217`	`221`	`*`
`218`	`222`	`* A C++11 lambda expression is a functor (function object). It is automatically`