item_flags2 bit 3 (unk_book) and building_flags bit 7 seem to identify items/buildings tied to 'Locations'

`item_flags2` bit 3

(This was last looked at in issue #251)

I noticed a cave spider thread with this unk_book flag set and thought it odd. It was in a coffer in my hospital. I checked other threads in stockpiles and the bit was clear.

I found these other items have the flag set (via gm-editor):

Instruments and goblets in chests in taverns
Instruments in chests in temples
plaster, thread and cloth in chests in hospital
books in bookshelves and on tables (!) in libararies
scrolls in chests in libraries

These items do not have the flag set:

clothing owned by a dwarf stored in a cabinet in their bedroom
books held by dwarfs in the library
meals on tables in the library
meals in barrels in a stockpile in the tavern
items on pedestals in temples
chests built in temples/taverns/hospitals

It seems to be set when an item is allocaed to and stored for use in a zone that is part of a named Location.

I suspect one use of this flag is to hide items from the Move to Depot screen.

`building_flags` bit 7

(Also mentioned in #532)

This led me to look at chests that are built in Locations and I noticed they all had bit 7 set in the building_flags.

Further investigation shows these buildings have the flag set:

chests, beds, tables and traction benches in hospitals
thrones, tables and chests in taverns
chests, some pedestals and altars in temples
thrones, tables, chests and bookcases in libraries
pedestals in guild halls

These buildings do not:

one pedestal and one chest in a temple (Unexpected. This temple had been removed and recreated a couple of times - so maybe a bug?)
beds, chests, cabinets, armor stands, weapon racks in bedrooms, offices, and dining rooms that do not belong to Locations

Summary

Both these bits seem to correlated with an item or building that belongs to a named Location. I propose these bits are both named in_location

DFHack / df-structures