Allow monsters besides Donald to talk in all branches.

<|amethyst> wheals:  dungeon, swamp, shoals, crypt, vaults, hell,
dis, zot, abyss, depths, and many portal vaults would work.

Other branches could not have monsters speaking based on their monster
type (though other key matches could work) ever since Donald's branch-
specific speech was added, in eb2694d6.
Don't hit an inifinte loop when casting IMB.