Macs2 shiftsize is depreciated

[pjmichalski]

Macs2 now uses extsize in place of the old shiftsize option. Mango still uses the shiftsize argument, which Macs2 fails to recognize and then crashes. I think it would be a good idea to update Mango with the proper arguments.

[dphansti]

Thanks for the suggestion. I just pushed a new version incorporating that change.