Log Message:
ocaml: Recognize NetBSD armv6 correctly in configure

While MACHINE_ARCH can be earmv6hf on NetBSD, configure has to match
what config.guess outputs, which is armv6.  For now, leave the old
earmv6/7 tokens, because this code inexplicably succeeded on earmv7hf.

With this, ocaml builds and builds a working unison, on earmv6hf
(RPI3).