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resources has been revoked by the registrant of the domain.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>

Add FILE_LICENCE declarations to almost all files that make up the
various standard builds of gPXE.

function name to appear within the objects even in non-asserting
builds.  (This could be considered a gcc bug.)

Removing __FUNCTION__ from assert() reduces the size of bin/blib.a by
around 2.5%!

linker_assert() defined as gPXE-specific.