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.

doc/fixes36.2

@@ -317,6 +317,8 @@ when splitting a stack where internal ID is used to make adjustment to
 when merging a stack where internal ID is used to adjust shop prices, always
 	keep the ID which induces the higher price (only matters when buying
 	from shop, not when selling; doesn't affect items already on bill)
+since knives became stackable in 3.6.0, fake player monsters could be given
+	multi-quantity stacks for weapons (scalpel, athame) they never throw
 
 
 Fixes to Post-3.6.1 Problems that Were Exposed Via git Repository