Limit the undo stack to 1000 items.
Limit the undo stack to 1000 items.

I'm not sure if this is needed, but I don't want to to expand without
bound.  I don't think users will need more than 1000 undo items anyways.

pculture/unisubs,pculture/unisubs,pculture/unisubs,pculture/unisubs