- make main dualboot creation function work on buffers instead of files.
This is to be used in beastpatcher and simplifies error handling a bit.
- prepare for building with beastpatcher.
- export dualboot creation function.
git-svn-id: svn://svn.rockbox.org/rockbox/trunk@22740 a1c6a512-1295-4272-9138-f99709370657