undo '-t n{s,m,h,d}' not implemented

[Thomas Nikolajsen]

undo -t flag only supports TID;
but manual page, undo(1), and usage() also says '-t n{s,m,h,d}';
will this be implemented before release?

Otherwise I will adjust undo(1) and usage() to what is currently implemented.

I think it is OK to just support '-t TID', as TID<->time is easy to get with '-i'.

 -thomas