[issue632] update libm for improved C99 compatibility

[Chris Turner]

Peter Avalos wrote:
> I'm not saying that we are C99 compliant in libm, but we're at least up-to-
> date with NetBSD.

Good stuff - I hadn't got around to another audio-apps build attempt, so
it hadn't bugged me again yet :)

Perhaps now some more things will build ..

Thanks,

- Chris