implement the -e option.

(Thanks to Jim McQuillan for this suggestion.)

(Problem observed by Clay McClure in VMware Fusion.)

order in which they occur.

require that we use drive 0x80, so it should probably be the default.

out-of-tree driver code.

to generate the initial transmission; this cuts off around 0.3s per
instantiated connection.

No Microsoft intellectual property was harmed in the production of
this code.

executing any image, not just a script.  (This will enable pxelinux to
use relative URIs, should it wish to.)

wasn't meant for my local "master" branch ;)
This reverts commit 373022108b.