Out-of-order data chunks handling and more

Out-of-order data chunks handling and more

This patch addresses the need to handle out-of-order data chunks
received by a peer. To do that effectively, we had to add the handling
of data chunks flags (E/B/U bit) to understand whether the stream is
fragmenting user-message data and in that case if a fragment is the
FIRST/MIDDLE/LAST one of a transmission.
The same patch also addresses the security requirement to have a HMAC
calculated and incorporated in the INIT_ACK and COOKIE_ECHO chunks. The
algorithm used is the HMAC-SHA1.

Change-Id: Ib6a9a80492e2aafe5c8480d6e02da895efe9f90b
Signed-off-by: Marco Varlese <marco.varlese@suse.com>