[Patch] Fix glibc testing with GCC 4.9 compiler

[Joseph Myers]

On Thu, 25 Feb 2016, Steve Ellcey  wrote:

> -  DIAG_IGNORE_NEEDS_COMMENT (5.0, "-Wmemset-transposed-args")
> +  DIAG_IGNORE_NEEDS_COMMENT (4.9, "-Wmemset-transposed-args")

Apart from the point that you can't change the __GNUC_PREREQ conditional, 
reducing the version in DIAG_IGNORE_NEEDS_COMMENT is always incorrect.  
The version there is the *most recent* version for which we know the 
pragma was needed - that is, old versions there indicate that the pragma 
should be revisited (in cases working around compiler warning bugs) when 
that version is no longer supported for building glibc.

-- 
Joseph S. Myers
joseph@codesourcery.com