Where are signal_can_redo() and signal_can_undo() methods?

["Yuriy Syrota" <ysyrota gmail com>]

Hello.

I notoced that current gtksourceviewmm lacks of signal_can_redo() and
signal_can_undo() methods in SourceBuffer class, but previous versions
have these methods. What was the reason to remove them and how can I
manage without these methods?

Thanks!
-- yura