Also renames lua/lua.hpp to lua/lua_global.hpp.
The previous name broke version auto-detection in sol2, which involves
calling `__has_include(<lua/lua.hpp>)`.
Implements a `require` function that supports built-in modules like so:
```lua
local log = require('devilutionx.log')
```
It falls back to reading from assets, so this loads `lua/user.lua`:
```lua
local user = require('lua.user')
```
The bytecode for the asset scripts is cached, in case we want to later
support multiple isolated environments.
There may be a simpler or better way to do this.
It's good enough for now until someone more knowledgeable
about Lua comes along.
Enabled only in Debug mode.
Runs Lua similar to the `lua` CLI.
Supports multiline input with Shift+Enter.
Missing features:
1. Scrollback.
2. Input history on up/down.
Open with backtick, close with Esc.
Gleb Mazovetskiy
staphen