Require GCC 4.3 or later to build glibc

[Roland McGrath]

> It appears current practice is not to mention regeneration of generated 
> files (such as INSTALL and configure) in ChangeLogs.  We could discuss 
> changing that to something more like GCC and Binutils, where the logs do 
> say "Regenerate." for generated files.

That was always the convention ("Regenerated.") and nobody ever discussed
changing it.  Some people have failed to observe it in the last few months.