Increase minimum Linux kernel version to 2.6.32.

Increase minimum Linux kernel version to 2.6.32.

This patch increases the minimum Linux kernel version for glibc to
2.6.32, as discussed in the thread starting at
<https://sourceware.org/ml/libc-alpha/2014-01/msg00511.html>.

This patch just does the minimal change to arch_minimum_kernel
settings (and LIBC_LINUX_VERSION, which determines the minimum kernel
headers version, as it doesn't make sense for that to be older than
the minimum kernel that can be used at runtime).  Followups would be
expected to do, roughly and not necessarily precisely in this order:

* Remove __LINUX_KERNEL_VERSION checks in kernel-features.h files
  where those checks are always true / always false for kernels 2.6.32
  and above.

* Otherwise simplify/improve conditionals in those files (for example,
  where defining once in the main file then undefining in
  architecture-specific files makes things clearer than having lots of
  separate definitions of the same macro), possibly fixing in the
  process cases where a macro should optimally have been defined for a
  given architecture but wasn't.  (In the review in preparation for
  this version increase I checked what the right conditions should be
  for all macros in the main kernel-features.h whose definitions there
  would have been affected by the increase - but I only fixed that
  subset of the issues found where --enable-kernel=2.6.32 would have
  caused a kernel feature to be wrongly assumed to be present, not any
  cases where a feature is not assumed but could be assumed.)

* Remove conditionals on __ASSUME_* where they can now be taken to be
  always-true, and the definitions when the macros are only used in
  Linux-specific files.

* Split more architectures out of the main kernel-features.h (like
  ex-ports architectures), once various of the architecture
  conditionals there have been eliminated so the new
  architecture-specific files are no larger than actually necessary.

Tested x86_64.

2014-03-27  Joseph Myers  <joseph@codesourcery.com>

	[BZ #9894]
	* sysdeps/unix/sysv/linux/configure.ac (LIBC_LINUX_VERSION):
	Change to 2.6.32.
	(arch_minimum_kernel): Change all 2.6.16 settings to 2.6.32.
	* sysdeps/unix/sysv/linux/configure: Regenerated.
	* sysdeps/unix/sysv/linux/microblaze/configure.ac: Remove file.
	* sysdeps/unix/sysv/linux/microblaze/configure: Likewise.
	* sysdeps/unix/sysv/linux/tile/configure.ac: Likewise.
	* sysdeps/unix/sysv/linux/tile/configure: Likewise.
	* README: Update reference to required Linux kernel version.
	* manual/install.texi (Linux): Update reference to required Linux
	kernel headers version.
	* INSTALL: Regenerated.