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resources has been revoked by the registrant of the domain.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 intention is to include near-verbatim copies of the EFI headers
required by gPXE.  This is achieved using the import.pl script in
src/include/gpxe/efi.

Note that import.pl will modify any #include lines in each imported
header to reflect its new location within the gPXE tree.  It will also
tidy up the file by removing carriage return characters and trailing
whitespace.