stmhal: Overhaul network drivers; has generic network protocol in C.
This patch overhauls the network driver interface. A generic NIC must provide a set of C-level functions to implement low-level socket control (eg socket, bind, connect, send, recv). Doing this, the network and usocket modules can then use such a NIC to implement proper socket control at the Python level. This patch also updates the CC3K and WIZNET5K drivers to conform to the new interface, and fixes some bugs in the drivers. They now work reasonably well.