Support script handlers implemented in Lua
Created by: bwh-sah
The second argument to a handlers is normally its opaque data pointer, but for script handlers it's a pointer to the script_fn (PREINSTALL or POSTINSTALL) indicating which phase it is being called for.
The Lua handler wrapper code always needs its opaque data pointer, so it currently can't be used to implement script handlers.
- Replace the two uses of the data parameter with two separate parameters
- Add support for script handlers in the Lua handler wrapper
- Add a missing definition to the Lua bindings that can be useful for script handlers