Access to the gpxe.org and etherboot.org domains and associated
resources has been revoked by the registrant of the domain.  Work
around this problem by renaming project from gPXE to iPXE, and
updating URLs to match.

Also update README, LOG and COPYRIGHTS to remove obsolete information.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

The initial PXE implementation in Etherboot had the goal of being
architecture-agnostic, but this goal has not been realised.

even when __atribute__ (( unused )) is correctly set...