Don't claim GCC predefines __POSIX__

[Carlos O'Donell]

On Fri, Feb 17, 2012 at 1:05 PM, Joseph S. Myers
<joseph@codesourcery.com> wrote:
> Bug 4596 notes that the claim in the manual that GCC predefines
> __POSIX__ on POSIX systems is wrong.  Thus, I propose this patch to
> remove that claim (not mentioning the #system(posix) alternative since
> GCC preprocessor assertions are deprecated).

I agree that the manual should document reality and your patch looks good.

I have no opinion on the usefulness of a __POSIX__ definition by GCC.

How do you test that you are on a POSIX compliant system?

Cheers,
Carlos.