Independent sessions on netlink sockets mixed state
in some common variables.

Allows to add more interface patterns to one common 'options'
section like:

interface "eth3", "eth4" { options common to eth3 and eth4 };

Also removes undocumented and unnecessary ability to specify
more interface patterns with different 'options' sections:

interface "eth3" { options ... }, "eth4" { options ... };

FreeBSD coded added. BSD cannot set BGP passwords itself.
This has to be done by external command.

When sending 'third party' BGP update, Bird used bogus link local
addresses instead of addresses it received before.

options.

Also removes code skipping SNPAs
(obsoleted by newer RFCs, should be ignored).

Under specific circumstances there might be two mixed-up
netlink sessions (one for scan, the other for route change
request). This patch separates netlink scans and requests
to two fds (and seq counters).

This should fix http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=428865

Old AS path maching supposes thath AS number appears
only once in AS path, but that is not true. It also
contains some bugs related to AS path sets.

New code does not use any assumptions about semantic
structure of AS path. It is asymptotically slower than
the old code, but on real paths it is not significant.

It also allows '?' for matching one arbitrary AS number.

Cryptographic authentication in OSPF is defective by
design - there might be several packets independently
sent to the network (for example HELLO, LSUPD and LSACK)
where they might be reordered and that causes crypt.
sequence number error.

That can be workarounded by not incresing sequence number
too often. Now we update it only when last packet was sent
before at least one second. This can constitute a risk of
replay attacks, but RFC supposes something similar (like time
in seconds used as CSN).

If a DBDES packet from a master to a slave is lost, then the old code
does not retransmit it and instead send a next one with the same
sequence number. That leads to silent desynchronization of LSA
databases.

Replaces old OSPF packet tracing messages with
uniform messages with packet dumps.

Prefix sets were broken beyond any repair and have to be reimplemented.
They are reimplemented using a trie with bitmasks in nodes.
There is also change in the interpretation of minus prefix pattern,
but the old interpretation was already inconsistent with
the documentation and broken.

There is also some bugfixes in filter code related to set variables.

Routes comming through pipe from primary to secondary table were
filtered by both EXPORT and IMPORT filters, but they should be
only filtered by EXPORT filters.

Missing macro leads to not calling some of protocol's
callbacks.

KRF_INSTALLED flag was not cleared during reconfiguration
that lead to not removing routes during reconfigure when
export rules changed.

We also should not try to remove routes we didi not installed,
on Linux this leads to warnings (as kernel checks route source
field and do not allow to remove non-bird routes) but we should
not rely on it.

AS4 optional attribute errors were handled by session
drop (according to BGP RFC). This patch implements
error handling according to new BGP AS4 draft (*)
 - ignoring invalid AS4 optional attributes.

(*) http://www.ietf.org/internet-drafts/draft-chen-rfc4893bis-02.txt