Updated ipxe to current tree, which is
540e5960dc6b49eacf367f7c319fd0546474b845:
Provide PXENV_FILE_EXIT_HOOK only for ipxelinux.0 builds
Removed all the backported patches and updated
boot_prompt_option.patch to apply against current ipxe.
Signed-off-by: Roger Pau Monne <roger.pau@entel.upc.edu>
Committed-by: Ian Jackson <ian.jackson.citrix.com>