Require GCC 4.6 or later to build glibc

[Roland McGrath]

> -GCC 4.4 or higher is required; as of this writing, GCC 4.6 is the
> -compiler we advise to use to build @theglibc{}.
> +GCC 4.6 or higher is required; as of release time, GCC 4.9 is the
> +newest compiler verified to work to build @theglibc{}.

I think it should say something more like:

GCC 4.6 or higher is required.  In general it is recommended to use the
newest version of the compiler that is known to work for building
@theglibc{}, as newer compilers usually produce better code.  As of release
time, GCC 4.9 is the newest compiler verified to work to build @theglibc{}.

> --- a/sysdeps/arm/sysdep.h
> +++ b/sysdeps/arm/sysdep.h
[...]
> --- a/sysdeps/x86_64/fpu/dla.h
> +++ b/sysdeps/x86_64/fpu/dla.h

I'd like these to be separate follow-on changes after the one that does
nothing but update the configure check and documentation.  The only real
reason is feeling anal today, but still.


Thanks,
Roland