This is the way u-boot reduces configured-out code. At Wolfgang
Grandegger and Wolfgang Denk's request, make libfdt conform.
Signed-off-by: Gerald Van Baren <vanbaren@cideas.com>
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.
