Don't use rt_walktree to delete routes

Some functions use rt_walktree to scan the routing table and delete
matched routes. However, we shouldn't use rt_walktree to delete
routes because rt_walktree is recursive to the routing table (radix
tree) and isn't friendly to MP-ification. rt_walktree allows a caller
to pass a callback function to delete an matched entry. The callback
function is called from an API of the radix tree (rn_walktree) but
also calls an API of the radix tree to delete an entry.

This change adds a new API of the radix tree, rn_search_matched,
which returns a matched entry that is selected by a callback
function passed by a caller and the caller itself deletes the
entry. By using the API, we can avoid the recursive form.

branches: 1.22.40;
Make it possible to register delayed radix tree head inits which
will be processed when the radix "subsystem" is initialized -- all
users must be attached before any inits to know the max keylength.
Use of link sets is no longer required, and only attached domains
need to be considered.

branches: 1.21.2;
Cosmetic: break a line, change some spaces to tabs, remove an extra
empty line.

branches: 1.20.6;
Bzero, Bcmp, and Bcopy are not used any more, so delete them.

branches: 1.19.28; 1.19.30; 1.19.32; 1.19.34;
Get rid of radix_node_head.rnh_walktree, because it is only ever
set to rn_walktree.

Introduce rt_walktree(), which applies a subroutine to every route
in a particular address family. Use it instead of rn_walktree()
virtually everywhere. This helps to hide the routing table
implementation.

branches: 1.18.2; 1.18.6; 1.18.8;
Clean this code up some.

Extract subroutine rn_delete1() to ease RADIX_MPATH integration,
should we ever do that.

Remove RN_DEBUG code that does not compile.

Join some lines of the type

type var1;
type var2;
type var3;

making

type var1, var2, var3.

Break lines of the type if (expr) stmt1; else stmt2; so that normal
people can read them.

don't leak kernel variable declarations to userland.

branches: 1.16.20; 1.16.22;
Multiple inclusion protection, as suggested by christos@ on tech-kern@
few days ago.

branches: 1.15.2;
- sprinkle const
- remove unneeded casts
- use more mem*() instead of b*() funcs.

ANSI-fy and some additional de-__P and constification.

Constify if.c radix.c and route.c (and fix related fallout).

Move UCB-licensed code from 4-clause to 3-clause licence.

Patches provided by Joel Baker in PR 22364, verified by myself.

branches: 1.11.24;
fix typo in function name (rn_satsifies_leaf -> satisfies). indent.
split rn_inithead() into two function - i'm putting some hook around here.

avoid namespace pollution by radix.h. the #ifndef _KERNEL portion was to
use radix.c in userland compilation, however, noone is using it.
(routed has its own radix.c)

branches: 1.9.20; 1.9.22; 1.9.32;
Sync with Lite2.

Net prototypes

Newer version from CSRG.

KERNEL -> _KERNEL

New RCS ID's, take two. they're more aesthecially pleasant, and use 'NetBSD'

Update to 4.4-Lite networking code, with a few local changes.

add rcs ids to everything, and clean up headers

Add consistent multiple-inclusion protection.

branches: 1.1.1;
Initial revision