Require GCC 4.6 or later to build glibc.

As discussed in the thread starting at
<https://sourceware.org/ml/libc-alpha/2014-10/msg00792.html>, and
continuing into November, this patch increases the minimum GCC version
for building glibc to 4.6 (there seemed to be no clear consensus for
4.7).  In particular, this allows us to use #pragma GCC diagnostic for
fine-grained warning control with -Werror (subject to establishing a
suitable policy for that use).  The documentation has a statement, as
requested, about the most recent GCC version tested for building
glibc, and I've updated <https://sourceware.org/glibc/wiki/Release> to
refer to updating that statement.  A NEWS entry is added for this
change, although previous such changes didn't get them.

Tested for x86_64 (testsuite, and that installed shared libraries are
unchanged by this patch).

	* configure.ac (libc_cv_compiler_ok): Require GCC 4.6 or later.
	* configure: Regenerated.
	* manual/install.texi (Tools for Compilation): Document a
	requirement of GCC 4.6 or later and that GCC 4.9 is the newest
	compiler verified to work.
	* INSTALL: Regenerated.

1 files changed, 6 insertions, 3 deletions

diff --git a/manual/install.texi b/manual/install.texi
index e1c2b9a..1eafb6e 100644
--- a/manual/install.texi
+++ b/manual/install.texi
@@ -372,10 +372,13 @@ recommend GNU @code{make} version 3.79.  All earlier versions have severe
 bugs or lack features.
 
 @item
-GCC 4.4 or newer, GCC 4.6 recommended
+GCC 4.6 or newer
 
-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.  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{}.
 
 You can use whatever compiler you like to compile programs that use
 @theglibc{}.