In the past, the headers "linux/if.h" and "net/if.h" were incompatible.
That means, we can either include one or the other, but not both.
This is fixed in the meantime, however the issue still exists when
building against older kernel/glibc.

That means, including one of these headers from a header file
is problematic. In particular if it's a header like "nm-platform.h",
which itself is dragged in by many other headers.

Avoid that by not including these headers from "platform.h", but instead
from the source files where needed (or possibly from less popular header
files).

Currently there is no problem. However, this allows an unknowing user to
include <net/if.h> at the same time with "nm-platform.h", which is easy
to get wrong.

By using nm_memdup().

Except in shared/nm-utils/nm-compat.c, which may not include
"shared/nm-utils/nm-shared-utils.h".

Normalize coding style by removing consecutive empty lines from C
sources and headers.

https://github.com/NetworkManager/NetworkManager/pull/108

Will be used next...

Routes are complicated.

`ip route add` and `ip route append` behaves differently with respect to
determine whether an existing route is idential or not.

Extend the cmp() and hash() functions to have a compare type, that
covers the different semantics.

NMIP4Config, NMIP6Config, and NMPlatform shall share one
NMDedupMultiIndex instance.

For that, pass an NMDedupMultiIndex instance to NMPlatform and NMNetns.
NMNetns than passes it on to NMDevice, NMDhcpClient, NMIP4Config and NMIP6Config.
So currently NMNetns is the access point to the shared NMDedupMultiIndex
instance, and it gets it from it's NMPlatform instance.

The NMDedupMultiIndex instance is really a singleton, we don't want
multiple instances of it. However, for testing, instead of adding a
singleton instance, pass the instance explicitly around.

Extend the support for the preferred source route option (RTA_PREFSRC)
to IPv6.