[Cin] Mask tool: everything to be done again!

[I'm sorry, I'm kidding :-) ] The mask tool has become really useful and powerful. I thank Sam and IgorB for the many inputs and tests; Phyllis for keeping GG calm [ ;-) ] and everything else; and GG because he is an incredible coder. CinGG is a great project because you are in charge of it (not to mention Pierre, MatN, Andrew-R, einhander, Olaf and many others...).