[Lazarus] Add notification to callstack change.

[Everton Vieira]

Hi there.

I know very little about notifications, and maybe what i know is wrong, so any help would be useful.

I`m trying to add some kind of notication that triggers an event when the callstack of the application is changed.

By example, the Application.onException is trigged when an exception happens, some event similar to triggers when the callstack is changed, in other words, when the execution go to the next line of the code.

Please help, any help will be usefull.