[sr-dev] acc, dialog: dialog duration for timed-out dialogs change

Hi,

I would like to propose a patch in which the dialog duration displayed in the cdrs is: /0 -> timed-out not acknowledged dialogs duration from creation to timeout -> timed-out acknowledged dialogs / I am still testing the solution for the master branch while tests pass on a previous version. Any comments on the code? (I am not particularly proud of the string defines in the dlg_cb.h, but am unsure where to include some const variable accessible to both acc and dialog to pass as calback param for dialog expiration)

Thank you, Lucian Balaceanu