refactor - give vars sensible names
Use vector rather than unordered_map for gl_collectionplex.

This makes gl data prep a bit faster.
Split the bbox collision detector into objects and tiles ones.

This improves drawing-prep performance by 10% right now
(stepped_pools -lne152), and paves the way for switching the
tile collision-detector to a (far) more space-efficient structure
in the future.
fix indentation of view_on_the_world::prepare_gl_data
refactor - move objects_to_draw and tiles_to_draw closer to their usages

This doesn't seem to hurt performance.  I was hoping it might help
because of space or time locality but it didn't
(pressure_tunnel -lne301)
Use single-dimensional C array for tiles in a worldblock.

This makes performance slightly better (maybe 4% prep time
improvement in stepped_pools -lne151), and may make future
code tricks simpler.
Speed up worldblock creation

This decreases our scenarios' creation time for me
by 50 ms out of 300-900 ms - so, a 1/6 to 1/18 (16% to 5%)
improvement.  (Tested on flat, pressure_tunnel, stepped_pools)

I anticipate
count_of_non_interior_non_air_tiles_here_
to be useful for other things in the future too.
fix bounds-checked-ints compile (-DPARANOID=ON)
Save more init time

This saves another 30 ms init time.

We decided to make worldblock data public:
they are a hacky performance thing anyway, and the abstraction
needed to make them a hacky, encapsulated performance thing
would obscure as much as it revealed.  The simple act of accessing
a 'worldblock' indicates you're doing something funny already.

So, use 'git grep' or such to find out who's mucking with the members.
rename tile data_ to tile_data_

In case we make it public related to specific code doing
performance tricks like uint64_t-at-a-time operation,
it'd be good to be a more unique name.  And it doesn't
hurt here.
refactor
Make 'tile' trivially-constructible.

This makes worldblock init slightly faster,
and paves the way to put tiles in unions easier/& also on compilers
that don't support unrestricted unions yet.
Make air always "interior".

We didn't need the information for air,
and it's simpler and faster to be able to check
collidability using just the interiorness bit.

(TODO - we might rename interior to !collidable someday)
Increase worldblock-creation perf more

By another 70ms (on the same scale as the other recent
commits), tested with 'flat' and 'stepped_pools'.
add worldblock util
Make tile_physics keep track of worldblock's count of interior tiles.

This means it stays updated, and also happens to mean that
worldblock doesn't have to compute it to initialize it!
(because tile_physics::set_tile_interiorness() is used in
initialization as well as during tile activity).
fix spaces I accidentally added
redo check_local_caches_cross_worldblock_neighbor

(This gives just a minor performance boost)

I'm in the process of moving all the CONTENTS_ONLY and
CONTENTS_AND_LOCAL_CACHES_ONLY initialization to worldblock code,
because it was already half there for performance and it works better
in one place stylistically.
(And interiorness is not a concept that's going to change much.)
worldblock: add useful comment from tile_physics
Move the rest of interiorness initialization into worldblock code.

This shaves off another 10-20 ms, also.