Signed-off-by: NWolfgang Denk <wd@denx.de>

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.

Changes to David Gibson's original source to fit into u-boot's
environment.  No functionality changes.

This adds the applicable libfdt source files (unmodified) and a README
to explain where the source came from.

This adds the applicable libfdt source files (unmodified) and a README
to explain where the source came from.