Function: task_stack (INT task-id [, INT include-line-numbers [, INT include-variables]) => LIST
Returns information like that returned by the `callers()' function, but for the suspended task with the given <task-id>; the <include-line-numbers> argument has the same meaning as in `callers()'. Raises E_INVARG if <task-id> does not specify an existing suspended task and E_PERM if the programmer is neither a wizard nor the owner of the specified task.
If include-line-numbers is passed and true, line numbers will be included.
If include-variables is passed and true, variables will be included with each frame of the provided task.