Change heap size from 128K to 512K to accommodate larger TCP windows.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>

Change the window size from 4K to 64K to have at least a hope of sane
WAN performance.  Retransmission cost is mostly related to timeouts,
not amount retransmitted, anyway.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>

Suppress the Ctrl+B banner and zero out the timeout.  It's not very
useful for an integrated product, and very visually annoying on NBP
chainload.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>

gPXE 1.0.0 has support for using the cached DHCP packet from the
previous PXE stack, so do that rather than doing another DHCP.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>

Using "lret $2" to return from an interrupt causes interrupts to be
disabled in the calling program, since the INT instruction will have
disabled interrupts.  Instead, patch CF on the stack and use iret to
return.

Interestingly, the original PC BIOS had this bug in at least one
place.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>

Update copyright notices.  Per agreement with my new employer, Intel
Corporation, add Intel copyright notices where appropriate.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>

Update gPXE to version 0.9.6+, from commit
277b84c6e7d49f3cf01c855007f591de8c7cb75f in the main gPXE repository.

The only differences is src/config/general.h which has a few protocols
added, and src/arch/i386/prefix/boot1a.S which was called boot1a.s in
the upstream repository.