changed major shlib versions in netbsd-9

[Greg Troxel <gdt%lexort.com@localhost>]

Perhaps my build is messed up, but I just updated along netbsd-9 and
netbsd-10 and rebuilt.

On -10, I got new shlib versions for bind and unbound libs.  That's ok
because 10 is not yet released.

On -9, I see in my destdir:

  -r--r--r--  1 gdt  wheel  143494 Mar 26 12:59 /usr/obj/gdt-9/destdir/amd64/usr/lib/libbind9.a
  lrwxr-xr-x  1 gdt  wheel      16 Mar 26 13:00 /usr/obj/gdt-9/destdir/amd64/usr/lib/libbind9.so -> libbind9.so.21.0
  lrwxr-xr-x  1 gdt  wheel      16 Jan 30 12:49 /usr/obj/gdt-9/destdir/amd64/usr/lib/libbind9.so.13 -> libbind9.so.13.0
  -r--r--r--  1 gdt  wheel   74720 Jan 30 12:49 /usr/obj/gdt-9/destdir/amd64/usr/lib/libbind9.so.13.0
  lrwxr-xr-x  1 gdt  wheel      16 Mar 26 13:00 /usr/obj/gdt-9/destdir/amd64/usr/lib/libbind9.so.21 -> libbind9.so.21.0
  -r--r--r--  1 gdt  wheel   95744 Mar 26 12:59 /usr/obj/gdt-9/destdir/amd64/usr/lib/libbind9.so.21.0
  -r--r--r--  1 gdt  wheel  147542 Mar 26 12:59 /usr/obj/gdt-9/destdir/amd64/usr/lib/libbind9_p.a

which makes we think we had a pullup with an ABI change.

I think this is tickets 1804, 1805.

Or, do we claim that these libs are private to bind, and thus this is
not an ABI change?

(I have not tried to boot this system - I'm at the stage where the build
failed because there are old files in destdir.  That's  not an error in
current, but it's irregular in 9.)