additional compiler hardening flags

[Alan Barrett]

On Fri, 17 Jan 2014, Corinna Vinschen wrote:
>Here's the first one:
>
>   ../../src/openbsd-compat/fmt_scaled.c:84:2: error: array subscript has type ‘char’ [-Werror=char-subscripts]
>     while (isascii(*p) && isspace(*p))
>     ^

If the openssh developers are interested in fixing this bug, I 
refer them to the spatch which I submitted several years ago, in
<https://lists.mindrot.org/pipermail/openssh-unix-dev/2010-August/028895.html>

--apb (Alan Barrett)