Move most arch/i386 files to arch/x86, and adjust the contents of the
Makefiles and the include/bits/*.h headers to reflect the new
locations.

This patch makes no substantive code changes, as can be seen using a
rename-aware diff (e.g. "git show -M5").

This patch does not make the pcbios platform functional for x86_64; it
merely allows it to compile without errors.

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

Relicense files for which I am the sole author (as identified by
util/relicense.pl).

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.

We seem to be having issues with various E820 memory maps.  These
problems are often difficult to reproduce, requiring access to the
specific system exhibiting the problem.

Add a facility for hooking in a fake E820 map generator, using an
arbitrary map defined in a C array, solely in order to be able to test
the map-mangling code against arbitrary E820 maps.