* add IO lib (adapted to Rockbox)
* remove old IO wrappers
* rework helloworld.lua to work with the IO lib
* do some stuff in helloworld.lua better (part of FS#10379, by James Callahan)
git-svn-id: svn://svn.rockbox.org/rockbox/trunk@21541 a1c6a512-1295-4272-9138-f99709370657