application init returns watchdog timeout, thus it can
control the rate at with the application idle function
is called (= at every first watchdog timeout).
Unused variables.
Reduce spi clock speed, apparently it was too fast.
Introduce shadow buffered frame counter. The buffered (incoming) frame
counter of the enc has the undesirable side-effect of keeping the
interrupt asserted as long as the counter is above 0. So we decrement
it all the way to zero everytime it's above zero and increment the shadow
frame counter to keep track. After this the (PKTIF) interrupt is cleared
and we can go into sleep mode and get woken by the interrupt being asserted
when a new frame arrives.
Cleanup / cosmetics / whitespace etc.
Make interrupt handling more robust.

Still has some debug code in it, needs to be cleaned up.
Trivial debugging adjustment.
Split RX/TX error handling, seems to work better.
De-inline some functions that might work differently depending on
compilation flags, includes, defines, etc. Now they're compiled just
once, which makes it less complex to debug.
Introduce function/data sections and linker garbage collection to
discard unused code and data, saves a few bytes.
Add stack (memory) usage monitor.
Rearrange to move mac-specific code into enc.c
Two delays seems to be necessary to get the clearing of the interrupt
flags register always working...
spi: now the spi can go up again
make watchdog_reset() inline again, and rename it more
appropriately to watchdog_rearm().
watchdog/util: make reset a simple watchdog timeout, so it can
test watchdog operation.
tcp4: workaround for connection remaining open locally
after remote completely shut down the connection, last
ack packet without fin would not reset the state for
the connection.
use libc functions wherever possible to simplify code.
New style of command processing.
Add stats command to new command framework.