fix github issue #170 - stacks of non-missiles

fix github issue #170 - stacks of non-missiles

Fixes #170

Monsters never throw athames or scalpels but some fake player monsters
on the Astral Plane are given those.  Since they're stackable the
quantity usually gets boosted but there's no point in having more than
one if they won't be thrown.

This could have been fixed by letting monsters throw those two items,
but I prevented the quantity from being boosted instead.