Changed _fdt_check_header() to fdt_check_header() and made it part of
the interface - it is a useful routine.
Also did some asthetics cleanup to the include files (headers).
Enhanced the formerly private function _fdt_next_tag() to allow stepping
through the tree, used to produce a human-readable dump, and made
it part of the published interface.
Also added some comments.
Gerald Van Baren