'RELENG_6_0_0_RELEASE'.

This commit was manufactured to restore the state of the 6.0-RELEASE image.

Clearly comment the assumptions on the structure of keys (addresses)
and masks, and introduce a macro, LEN(p), to extract the size of these
objects instead of using *(u_char *)p which might be confusing.

Comment the confusion in the types used to pass around pointers
to keys and masks, as a reminder to fix that at some point.

Add a few comments on what some functions do.

Comment a probably inefficient (but still correct) section of code
in rn_walktree_from()

The object code generated after this commit is the same as before.

At some point we should also change same variable identifiers such
as "t, tt, ttt" to fancier names such as "root, left, right" (just
in case someone wants to understand the code!), replace misspelling
of NULL as 0, remove 'register' declarations that make little sense
these days.

where it is used, and replace R_Malloc with R_Zalloc in a couple
of places removing the corresponding bzero()'s

+ remove useless wrappers around bcmp(), bcopy(), bzero().
  The code assumes that bcmp() returns 0 if the size is 0, but
  this is true for both the libc and the libkern versions.

+ nuke Bcmp, Bzero, Bcopy from radix.h now that nobody uses them anymore.

license, per letter dated July 22, 1999 and email from Peter Wemm,
Alan Cox and Robert Watson.

Approved by: core, peter, alc, rwatson

be happening if we didn't stop compiling with -fno-strict-aliasing.

Some style fixes requested by bde.

incorporated by UCB as revision 8.5.  Do a diff reduction.