Reduce kernel-features.h duplication.

This patch reduces duplication between different architectures'
kernel-features.h files by making the architecture-independent file
define various macros unconditionally (instead of only for a
particular list of architectures), with the architecture-specific
files then undefining the macros if necessary.

Specifically, __ASSUME_O_CLOEXEC (O_CLOEXEC flag to open) and
__ASSUME_SOCK_CLOEXEC (SOCK_NONBLOCK and SOCK_CLOEXEC flags to socket)
are supported on all architectures as of 2.6.32 or the minimum kernel
version for the architecture if later.  For __ASSUME_IN_NONBLOCK,
__ASSUME_PIPE2, __ASSUME_EVENTFD2, __ASSUME_SIGNALFD4 and
__ASSUME_DUP3, the relevant syscalls were added for alpha in 2.6.33
but otherwise the features are available as of 2.6.32.  For
__ASSUME_UTIMES, support is everywhere in 2.6.32 except for
asm-generic architectures and hppa.

Although those were the main cases of duplication among
kernel-features.h files, some other cases of unnecessary definitions
were also cleaned up: the hppa file defined various macros that were
either no longer used at all, or defined by the main file by default
anyway, the ia64 file had duplicative definitions of __ASSUME_PSELECT
and __ASSUME_PPOLL, while mips had such a definition of
__ASSUME_IPC64.

Really, rather than being defined in the main file then undefined for
asm-generic architectures, __ASSUME_UTIMES should become an
hppa-specific macro.  Given that __ASSUME_ATFCTS and
__ASSUME_UTIMENSAT are now always true, the only live __ASSUME_UTIMES
conditional is in sysdeps/unix/sysv/linux/utimes.c, which is not used
for asm-generic architectures.  I think the desired state would be an
hppa-specific file (that includes sysdeps/unix/sysv/linux/utimes.c if
__ASSUME_UTIMES, and otherwise has fallback code), with the fallback
code being removed from the main utimes.c.  But I think that's most
reasonably a separate cleanup once __ASSUME_ATFCTS and
__ASSUME_UTIMESAT have both had conditional code cleaned up.

Given this patch, I think it's straightforward to move non-ex-ports
architectures to having their own kernel-features.h files, like
ex-ports architectures, rather than conditionals in the main file
(i.e., such a move won't require the architecture-specific file to
contain anything that isn't genuinely architecture-specific), and
would encourage architecture maintainers to do so.

Tested x86_64 that the installed shared libraries are unchanged by
this patch.  Note that on some architectures this *will* cause
__ASSUME_* macros to be defined in cases where they weren't previously
but should have been (but this is just optimization, not a fix to a
user-visible bug, so doesn't need a bug report in Bugzilla).

	* sysdeps/unix/sysv/linux/kernel-features.h (__ASSUME_UTIMES):
	Define unconditionally.
	(__ASSUME_O_CLOEXEC): Likewise.
	(__ASSUME_SOCK_CLOEXEC): Likewise.
	(__ASSUME_IN_NONBLOCK): Likewise.
	(__ASSUME_PIPE2): Likewise.
	(__ASSUME_EVENTFD2): Likewise.
	(__ASSUME_SIGNALFD4): Likewise.
	(__ASSUME_DUP3): Likewise.
	* sysdeps/unix/sysv/linux/aarch64/kernel-features.h
	(__ASSUME_DUP3): Do not define.
	(__ASSUME_EVENTFD2): Likewise.
	(__ASSUME_IN_NONBLOCK): Likewise.
	(__ASSUME_O_CLOEXEC): Likewise.
	(__ASSUME_PIPE2): Likewise.
	(__ASSUME_SIGNALFD4): Likewise.
	(__ASSUME_SOCK_CLOEXEC): Likewise.
	(__ASSUME_UTIMES): Undefine.
	* sysdeps/unix/sysv/linux/alpha/kernel-features.h
	(__ASSUME_UTIMES): Do not define.
	(__ASSUME_O_CLOEXEC): Likewise.
	(__ASSUME_SOCK_CLOEXEC): Likewise.
	(__ASSUME_IN_NONBLOCK): Undefine if [__LINUX_KERNEL_VERSION <
	0x020621] instead of defining if [__LINUX_KERNEL_VERSION >=
	0x020621].
	(__ASSUME_PIPE2): Likewise.
	(__ASSUME_EVENTFD2): Likewise.
	(__ASSUME_SIGNALFD4): Likewise.
	[__LINUX_KERNEL_VERSION < 0x020621] (__ASSUME_DUP3): Undefine.
	* sysdeps/unix/sysv/linux/arm/kernel-features.h (__ASSUME_UTIMES):
	Do not define.
	(__ASSUME_EVENTFD2): Likewise.
	(__ASSUME_SIGNALFD4): Likewise.
	* sysdeps/unix/sysv/linux/hppa/kernel-features.h
	(__ASSUME_32BITUIDS): Likewise.
	(__ASSUME_TRUNCATE64_SYSCALL): Likewise.
	(__ASSUME_IPC64): Likewise.
	(__ASSUME_ST_INO_64_BIT): Likewise.
	(__ASSUME_GETDENTS64_SYSCALL): Likewise.
	[__LINUX_KERNEL_VERSION < 0x030e00] (__ASSUME_UTIMES): Undefine.
	* sysdeps/unix/sysv/linux/ia64/kernel-features.h
	(__ASSUME_UTIMES): Do not define.
	(__ASSUME_PSELECT): Likewise.
	(__ASSUME_PPOLL): Likewise.
	(__ASSUME_O_CLOEXEC): Likewise.
	(__ASSUME_SOCK_CLOEXEC): Likewise.
	(__ASSUME_IN_NONBLOCK): Likewise.
	(__ASSUME_PIPE2): Likewise.
	(__ASSUME_EVENTFD2): Likewise.
	(__ASSUME_SIGNALFD4): Likewise.
	(__ASSUME_DUP3): Likewise.
	* sysdeps/unix/sysv/linux/m68k/kernel-features.h
	(__ASSUME_UTIMES): Likewise.
	(__ASSUME_O_CLOEXEC): Likewise.
	(__ASSUME_SOCK_CLOEXEC): Likewise.
	(__ASSUME_IN_NONBLOCK): Likewise.
	(__ASSUME_PIPE2): Likewise.
	(__ASSUME_EVENTFD2): Likewise.
	(__ASSUME_SIGNALFD4): Likewise.
	(__ASSUME_DUP3): Likewise.
	* sysdeps/unix/sysv/linux/microblaze/kernel-features.h
	(__ASSUME_UTIMES): Likewise.
	(__ASSUME_O_CLOEXEC): Likewise.
	(__ASSUME_SOCK_CLOEXEC): Likewise.
	(__ASSUME_IN_NONBLOCK): Likewise.
	(__ASSUME_PIPE2): Likewise.
	(__ASSUME_EVENTFD2): Likewise.
	(__ASSUME_SIGNALFD4): Likewise.
	(__ASSUME_DUP3): Likewise.
	* sysdeps/unix/sysv/linux/mips/kernel-features.h (__ASSUME_IPC64):
	Likewise.
	(__ASSUME_UTIMES): Likewise.
	(__ASSUME_EVENTFD2): Likewise.
	(__ASSUME_SIGNALFD4): Likewise.
	* sysdeps/unix/sysv/linux/tile/kernel-features.h
	(__ASSUME_O_CLOEXEC): Likewise.
	(__ASSUME_SOCK_CLOEXEC): Likewise.
	(__ASSUME_IN_NONBLOCK): Likewise.
	(__ASSUME_PIPE2): Likewise.
	(__ASSUME_EVENTFD2): Likewise.
	(__ASSUME_SIGNALFD4): Likewise.
	(__ASSUME_DUP3): Likewise.
	(__ASSUME_UTIMES): Undefine.

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