tribute passage limit

tribute passage limit

Death Quotes have reached the current limit of 30 passages per 'book'.
Instead of increasing that, change the selection code to be able to
operate on a subset (dropped from 30 down to 20) at a time while
keeping the excess available for later selection.

Chatting with Death (more than 20 times since he also delivers non-
tribute messages) should cycle through 20 of his 30 passages without
repeating.  After that, another subset of 20 out of the 30 will be
chosen, independent of the first set so might contain all, some, or
none of the 10 that left out before.