way everything remains consistent if the probe() ends up creating child
devices.

Call netdevice's poll() and transmit() methods only when device is open.

based on the device size.

that some targets send.

anywhere other than offset 0 within the EEPROM, so we have to put our
settings at 0x100 instead.

this can probably be optimised down quite a lot.

device.

Separated the mechanisms of non-volatile storage access and non-volatile
stored options.

a word length.

that don't provide the full flexibility of a bit-bashing interface.

Temporarily hacked rtl8139.c to use the new interface.

Added CHAP authentication

defined in vsprintf.h.  (This may change, since vsprintf.h is a
non-standard name, but for now it's the one to use.)

There should be no need to include vsprintf.h just for DBG() statements,
since include/compiler.h forces it in for a debug build anyway.