kernel32: Disable diagnostics when testing corner cases in test_heap().

[Henri Verbeet]

On 21 February 2017 at 15:03, Erich E. Hoover
<erich.e.hoover at wine-staging.com> wrote:
> I'm not convinced that this statement is true.  For example, while
> "~(SIZE_T)0 - 7" gives us 4294967288 (matching what is indicated by
> the warning), HeapReAlloc accepts a SIZE_T.  So, this should support a
> maximum value of 4294967295 (not 2147483647).  This says to me that
> gcc thinks SIZE_T is a signed value instead of an unsigned value, do
> you have any idea why this might be the case?
>
It doesn't check against the type's size, but against the size
specified by -Walloc-size-larger-than=. If that's not explicitly set,
that's PTRDIFF_MAX.