Conflicts:
common/arch/sdl/window.cpp - Remove unused EVENT_WINDOW_CLOSED and w_callback local var
common/ui/dialog.cpp - Remove unused EVENT_WINDOW_CLOSED
Allow dcx::UI_DIALOG struct to be subclassed step 3. This step adds the destructor and makes sure the dialog is only deleted within the main dialog handler if the specific handler didn't return window_event_result::deleted.
Replace delete dcx::window kludge with a better solution: instead of requiring every handler to delete the window, add a window_event_result::deleted, which gets returned if the window was deleted by the handler, so window_close knows not to attempt to delete it again.
Allow dcx::UI_DIALOG struct to be subclassed step 1. This step renames and reconfigures untyped_ui_dialog_create in dialog.cpp to be the main constructor. Also adds a template constructor that allows an event handler that takes a subclass of UI_DIALOG.
Allow dcx::window struct to be subclassed step 3. This step adds the window destructor and both requires and implements the window to be deleted by the event handler/client in all cases.
Rename ui_create_dialog<void *> specialization with free function
untyped_ui_create_dialog. GCC 4.6 incorrectly considers a
specialization to be a redundant declaration, causing a
-Wredundant-decls failure with the specialization form.
Fixes: be041a9cfc ("Add type checking for ui_create_dialog")