This commit introduces Raycast, a Lua user object, which can be
used to perform a raycast on the map. The ray is continuable, so one can
also get hidden nodes (for example to see trough glass).
* Load client-side mods into memory before executing them.
This removes the remaining filesystem access that client-sided mods had and it will hopefully make then more secure.
* Lua Virtual filesystem: don't load the files into memory just scan the filenames into memory.
* Fix the issues with backtrace
* fix most of the issues
* fix code style.
* add a comment
This unifies the settings APIs.
This also unifies the sync and async registration APIs, since the async
registration API did not support adding non-functions to the API table.
