Use correct script name for init script correcting the traceback output

[ian-m-carr]

The current code uses the module script name for the init script content resulting in a confusing debug.traceback content.

This patch uses the in_init_script to build the correct name for the script resulting in a traceback like this:

xlua: traceback: [string "init.lua"]:240: bad argument #2 to 'XLuaWrapCommand' (nil not allowed for callback)
stack traceback:
	[C]: at 0x7ff8291f5660
	[C]: in function 'XLuaWrapCommand'
	[string "init.lua"]:240: in function 'wrap_command'
	[string "scripts/C90_sys/C90_sys.lua"]:3958: in function 'fn'
	[string "init.lua"]:498: in function <[string "init.lua"]:474>