Manager: ignore return value on dev attach
Merge branch 'master' of git://github.com/mirage/mirage-net
switch to encouraging scatter-gather all the time, rather than playing tricks with packet header buffers. This simplifies the output stack and removes the need for the `Frame` module.
(still a WIP)
Install the packed `cmx` along with the `cmxa` to ensure that the compiler can do cross-module optimization (this is not a fatal error, but will impact performance if the `cmx` file is not present).
IPv4: fix the header length calculation

By convention we have a single header buffer containing ethernet/IP/TCP...
and a list of payload fragments. When we calculat the IPv4 header length
we must sum the length of the payload fragments *and* the length of everything
in the header buffer except the ethernet header length.

This fixes the bug where TCP headers appear to be missing in wireshark;
they are actually present on the wire but the parser is obeying the IP
header length field and truncating the packet before display.
Merge pull request #17 from djs55/fix-ipv4-header-len

IPv4: fix the header length calculation