This commit is only move code around without changing it.
The reason behind this is to make review process easier
by allowing the reviewer to simply ignore all code movements.
changes:
1. rename scripting.c to eval.c
2. introduce and new file, script_lua.c, and move parts of Lua
functionality to this new file. script_lua.c will eventually
contains the shared code between legacy lua and lua engine.
This commit does not compiled on purpose. Its only purpose is to move
code and rename files.
