Function to decode distribution header

[Erik Rigtorp]

git fetch git://github.com/rigtorp/otp.git ei_decode_msg

commit 01821ee1945370504d37edc72de8de84d2d40cd8
Author: Erik Rigtorp <erik@REDACTED>
Date:   Wed Mar 10 16:39:22 2010 +0100

    Add function to decode distribution header

    There is currently no way to use erl_interface with non-blocking
    sockets. This patch adds a function ei_decode_header() that can decode
    the distribution header of a message sent to a C-node. This will allow a
    C-node to receive messages using an asynchronous event loop.

Next step is to add a ei_send() function that would write to a supplied buffer.