[m-rev.] for review: replace a binop with two unops

[Peter Wang]

On Wed, 14 Mar 2018 06:36:22 +1100 (AEDT), "Zoltan Somogyi" <zoltan.somogyi at runbox.com> wrote:
> Use unary ops to access the halves of dwords.
> 
> compiler/builtin_ops.m:
>     Replace the float_word_bits binary op with two unary ops,
>     dword_float_get_word[01]. The unchanged operand represents the address
>     of the double word. The only two values of the deleted operand that
>     made sense were the constants 0 and 1. Replacing the binary op
>     with two unary ops encodes this invariant in the types.

That's fine.

Peter