Internet on FIRE

There can be multiple primary addresses with different scopes
and only the highest scope one has IA_PRIMARY set, so report
the remaining ones as "Unselected".

Bugfix in iface_patts_equal.
When both patterns were NULL strcmp it sigfaulted.

More documentation.

Removed a lot of unused variables.

Please try compiling your code with --enable-warnings to see them. (The
unused parameter warnings are usually bogus, the unused variable ones
are very useful, but gcc is unable to control them separately.)

Fix stupid bug in neighbor cache.

Added tracing of interface events.

Rewrote interface type detection logic. The `unnumbered' flag is now per
address, not per interface (hence it's ifa->flags & IA_UNNUMBERED) and
should be set reliably. IF_MULTIACCESS should be fixed now, but it isn't
wise to rely on it on interfaces configured with /30 prefix.

Reworked proto lists -- each proto is now in two lists: the global one
(proto_list) and per-type one (original lists). A lot of things simplified.

Implemented `disable', `enable' and `restart' CLI commands.

Introduced new protocol-dependent integer field `aux' to struct neighbor.

Added few basic commands: show status, show interfaces [summary],
show protocols (incomplete).

Cleaned up handling of interface patterns:

o  Parsing of interface patterns moved to generic code,
      introduced this_ipatt which works similarly to this_iface.
   o  Interface patterns now support selection by both interface
      names and primary IP addresses....

I rewrote the interface handling code, so that it supports multiple
addresses per interface (needed for example for IPv6 support).

Visible changes:

o struct iface now contains a list of all interface addresses (represented
by struct ifa), iface->addr points to the primary address (if any)....

o The if_change_too_big_p change was too high-spirited. Fixed.
o Introduced if_find_by_index()
o Recognizing two types of interface updates: full update (starting with
if_start_update(), ending with if_end_update(), guaranteed to see
all existing interfaces) and a partial update (only if_update(),...

Parameter order for the proto->if_notify hook was different in the include
file and different in reality. Decided to use the same order as we do
for proto->rt_notify (i.e., first new value and second the old one).

When protocols go down, prune the neighbor list.

struct proto again contains instance name (a copy of proto->cf->name).

die() -> bug() where appropriate.

Added functions for manipulating interface name pattern lists:

o  iface_patt_match(list, iface) -- match interface against list
   o  iface_patts_equal(a, b, c) -- compare whether two pattern lists are
      equal or not. c(x,y) is called for comparison of protocol-dependent...

Solve chicken-and-egg problems with protocol startup. We now queue all inactive
protocols and don't send route/interface updates to them and when they come up,
we resend the whole route/interface tables privately.

Removed the "scan interface list after protocol start" work-around.

Now sending IF_CHANGE_CREATE when a new interface appears and IF_CHANGE_UP
only if it's really up.

- Rewrote whole interface logic. Removed support for multiple addresses per
interface since it makes much trouble everywhere. Instead, we understand
secondary addresses as subinterfaces.

- In case interface addresses or basic flags change, we simply convert it...