Add ability for network devices to flag link up/down state to the
networking core.

Autobooting code will now wait for link-up before attempting DHCP.

IPoIB reflects the Infiniband link state as the network device link state
(which is not strictly correct; we also need a succesful IPoIB IPv4
broadcast group join), but is probably more informative.

Allow for settings to be described by something other than a DHCP option
tag if desirable.  Currently used only for the MAC address setting.

Separate out fake DHCP packet creation code from dhcp.c to fakedhcp.c.

Remove notion of settings from dhcppkt.c.

Rationalise dhcp.c to use settings API only for final registration of the
DHCP options, rather than using {store,fetch}_setting throughout.

Add dedicated functions create_dhcpdiscover(), create_dhcpack() and
create_proxydhcpack() for use by external code such as the PXE preboot
code.

Register ProxyDHCP options under the global scope "proxydhcp".

Unregister previously-acquired DHCP and ProxyDHCP settings when DHCP
succeeds.

Some shuffling around of the image management code; this needs tidying up.

initiator.  This table needs to be replaced by something similar to
iBFT (i.e. scanned for and identified by signature, rather than being
at a fixed address), but it works for now.

iSCSI hack.

really ugly hack at present, but that doesn't hugely matter since I'm
aiming to change the interface to iSCSI devices anyway within the next
week.

via UNDI API and also by ifstat command; may be useful for debugging.

allows us to avoid execution loops without having to hack around the
image registration order.

output buffering defintions and the like)

download

other protocol won't work at the moment.

reflect the fact that they allocate and deallocate user memory (i.e.
things reached through a userptr_t).

of blocking on asynchronous operations, when that isn't an important
aspect of the code.

it as a fallback network device rather than an explicitly forced network
device.

Clear routing table entries before re-attempting DHCP.

exception rather than the rule; we may as well keep things clean for other
protocols.

will enable us to cascade async operations, which is necessary in order to
properly support DNS.  (For example, an HTTP request may have to redirect
to a new location and will have to perform a new DNS lookup, so we can't
just rely on doing the name lookup at the time of parsing the initial
URL).

Anything other than HTTP is probably broken right now; I'll fix the others
up asap.

took out the contract to eventually call efree() when it called fetch().

Maintain the most recently loaded image at the start of the list, so that
imgautoselect() will pick it.

returns the allocated buffer.

"kernel".