Use PacketGetfromAlloc() for packet allocation instead of SCMalloc.

Only changed in one file for testing.
More PacketGetFromMalloc() to allocate packets.
Clear the PKT_ALLOC flag when storing Packets into the Packet pool.

The PKT_ALLOC flag is set by PacketGetFromAlloc(), which needs to be
cleared for Packets in the Packet Pool, so clear the flag here.
Update configure.ac to detect Tile architecture.

Detect if the architecture supports the Tilera mPipe packet processing
hardware. It it does, add the requried libraries and define HAVE_MPIPE.