Drop instance of ABILITY_CAPTION I forgot to remove
Use a single global 'helper' table in Lua instead of file locals
Add a couple of Lua script file description blocks
Add hex geometry Lua functions from AtS, originally by mattsc

This code is taken from mattsc's AI-demos add-on. See
<https://github.com/mattsc/AI-demos/blob/master/lua/ai_helper.lua>.
Raise engine version requirement to 1.11.11
Add [invert_direction] WML action from AtS
Add [store_direction] WML action from AtS
Add [set_facing] WML action a.k.a. Unit-Facing-o-Matic-3000, from AtS
Add simple wrapper macros for the [set_facing] WML action, from AtS
Replace SET_FACING macro with FACE_DIRECTION, drop SET_FACING
Remove built-in Falcon, we use the Khalifate version now