ns32k configury

Since ns32k-netbsd is as yet not removed, just marked obsolete,
the target should still be accepted with --enable-obsolete.

I also enabled ns32k-openbsd in ld since there doesn't seem to be a
good reason why that target is not supported there but is elsewhere.

bfd/
	* config.bfd: Allow ns32k-netbsd.
ld/
	* configure.tgt: Allow ns32k-openbsd.