The old network stack has some bad limitations:

- network commands are required to call NetLoop() which only returns when
  the network layer wants to. Instead we now use a net_poll() function which
  returns after handling one packet (or immediately if no packet is
  available).
- There can be only one packet handler which makes it impossible to handle
  multiple connections
- CamelCaseMakesItHardToRead

The new network stack is implemented as a parallel universe. Currently all
commands still use the old stack. They are converted in subsequent patches.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>