Heads-Up: 64-bit clean routing socket diffs

[Matt Thomas <matt%3am-software.com@localhost>]

At http://www.netbsd.org/~matt/route64-diffs.txt is a set of diffs against 
NetBSD that will add a 64-bit clean routing socket.  This allows 32-bit 
programs which use the routing socket or PF_ROUTE sysctls to work when using a 
64-bit kernel under COMPAT_NETBSD32.  This has required using fixed sized types 
in all routing messages, aligning things to 64-bit boundaries, and thusly 
bumping RTM_VERSION by 1 to 4.

Since that would cause existing programs to not work, I've also assigned 
AF_ROUTE/PF_ROUTE a new number.  To use the new 64-bit clean routing socket, 
you will need to recompile all tools.  

If your kernel has COMPAT_50, a old routing socket will provided for existing 
tools using the old PF_ROUTE value to use.  I've booted a new kernel of a 5.0 
userland and it worked fine.

I plan on committing with (with a version bump of the kernel) in a day or two.

After these changes are committed, with COMPAT_NETBSD32, you can run with a 
complete 32-bit userland on 64-bit kernels.  (except for kernel grovelers will 
fail but beyond the scope of COMPAT_NETBSD32).