Turret's barrel "points straight up" in tech room and briefing popup

[tomimaki]

Before: After:

88c1d8a02a9062c394262aca3888e2debb15c22a is the first bad commit
commit 88c1d8a02a9062c394262aca3888e2debb15c22a
Author: Goober5000 <ipw47@mailbox.org>
Date:   Sat Dec 12 02:04:02 2020 -0500

    consolidate model instance code

 code/ai/aibig.cpp                     |   3 +-
 code/ai/aicode.cpp                    |   5 +-
 code/ai/aiturret.cpp                  |  13 +-
 code/decals/decals.cpp                |  11 +-
 code/hud/hudtarget.cpp                |   1 -
 code/menuui/techmenu.cpp              |  21 +-
 code/mission/missionparse.cpp         |   2 +-
 code/missionui/redalert.cpp           |   2 +-
 code/model/model.h                    |  53 ++---
 code/model/modelanim.cpp              |  54 ++---
 code/model/modelcollide.cpp           |  13 +-
 code/model/modelread.cpp              | 381 ++++++++++++----------------------
 code/model/modelrender.cpp            |  35 +---
 code/network/multi_obj.cpp            |  24 ++-
 code/network/multimsgs.cpp            |  16 +-
 code/object/collideshipship.cpp       |  10 +-
 code/parse/sexp.cpp                   |  40 ++--
 code/scripting/api/objs/subsystem.cpp |  10 +-
 code/ship/ship.cpp                    |  61 +++---
 code/ship/ship.h                      |   4 +-
 code/ship/shipfx.cpp                  |  31 +--
 code/ship/shiphit.cpp                 |   6 +-
 22 files changed, 352 insertions(+), 444 deletions(-)

Check Orion, Deimos or anything with barrels. Before this commit they were at default position defined in table.

[Goober5000]

I think this is because the tech room doesn't use a model instance. Will fix that.