[dcplusplus-devel] patch: update the main window title

[poy <po...@12...>]

update the main window title when the active child frame changes.
i added an event called onTitleChanged in WidgetTabView, not using any 
dispatcher struct but simply with a callback function.
also, i'm not sure about that static_cast from Widget* to WidgetWindow*, but 
it works fine here...

poy