Remove __need macros from signal.h.

Remove __need macros from signal.h.

The types affected are __sig_atomic_t, sig_atomic_t, __sigset_t,
sigset_t, sigval_t, sigevent_t, and siginfo_t. __sig_atomic_t is a
scalar, so it's now directly available from bits/types.h.  The others
get bits/types/ headers.

Side effects include: There have been small changes to which
non-signal headers expose which subset of the signal-related types.
A couple of architectures' nested siginfo_t fields had to be renamed
to prevent undesired macro expansion.  Internal code that wants to
manipulate signal masks must now include <sigsetops.h> (which is not
installed) and should be aware that __sigaddset, __sigandset,
__sigdelset, __sigemptyset, and __sigorset no longer return a value
(unlike the public API).  Relatedly, the public signal.h no longer
declares any of those functions.  The obsolete sigmask() macro no
longer has a system-specific definition -- in the cases where it
matters, it didn't work anyway.

New Linux architectures should create bits/siginfo-arch.h and/or
bits/siginfo-consts-arch.h to customize their siginfo_t, rather than
duplicating everything in bits/siginfo.h (which no longer exists).
Add new __SI_* macros if necessary.  Ports to other operating systems
are strongly encouraged to generalize this scheme further.

	* bits/sigevent-consts.h
	* bits/siginfo-consts.h
	* bits/types/__sigset_t.h
	* bits/types/sigevent_t.h
	* bits/types/siginfo_t.h
	* sysdeps/unix/sysv/linux/bits/sigevent-consts.h
	* sysdeps/unix/sysv/linux/bits/siginfo-consts.h
	* sysdeps/unix/sysv/linux/bits/types/__sigset_t.h
	* sysdeps/unix/sysv/linux/bits/types/sigevent_t.h
	* sysdeps/unix/sysv/linux/bits/types/siginfo_t.h:
	New system-dependent bits headers.

	* sysdeps/unix/sysv/linux/bits/siginfo-arch.h
	* sysdeps/unix/sysv/linux/bits/siginfo-consts-arch.h
	* sysdeps/unix/sysv/linux/ia64/bits/siginfo-arch.h
	* sysdeps/unix/sysv/linux/ia64/bits/siginfo-consts-arch.h
	* sysdeps/unix/sysv/linux/mips/bits/siginfo-arch.h
	* sysdeps/unix/sysv/linux/sparc/bits/siginfo-arch.h
	* sysdeps/unix/sysv/linux/tile/bits/siginfo-arch.h
	* sysdeps/unix/sysv/linux/tile/bits/siginfo-consts-arch.h
	* sysdeps/unix/sysv/linux/x86/bits/siginfo-arch.h:
	New Linux-only system-dependent bits headers.

	* signal/bits/types/sig_atomic_t.h
	* signal/bits/types/sigset_t.h
	* signal/bits/types/sigval_t.h:
	New non-system-dependent bits headers.

	* sysdeps/generic/sigsetops.h
	* sysdeps/unix/sysv/linux/sigsetops.h:
	New internal headers.

	* include/bits/types/sig_atomic_t.h
	* include/bits/types/sigset_t.h
	* include/bits/types/sigval_t.h:
	New wrappers.

	* signal/sigsetops.h
	* bits/siginfo.h
	* bits/sigset.h
	* sysdeps/unix/sysv/linux/bits/siginfo.h
	* sysdeps/unix/sysv/linux/bits/sigset.h
	* sysdeps/unix/sysv/linux/ia64/bits/siginfo.h
	* sysdeps/unix/sysv/linux/mips/bits/siginfo.h
	* sysdeps/unix/sysv/linux/s390/bits/siginfo.h
	* sysdeps/unix/sysv/linux/sparc/bits/siginfo.h
	* sysdeps/unix/sysv/linux/tile/bits/siginfo.h
	* sysdeps/unix/sysv/linux/x86/bits/siginfo.h:
	Deleted.

	* signal/Makefile, sysdeps/unix/sysv/linux/Makefile:
	Update lists of installed headers.

	* posix/bits/types.h: Define __sig_atomic_t here.
	* signal/signal.h: Use the new bits headers; no need to handle
	__need_sig_atomic_t nor __need_sigset_t.  Don't use __sigmask
	to define sigmask.
	* include/signal.h: No need to handle __need_sig_atomic_t
	nor __need_sigset_t.  Don't define __sigemptyset.

	* io/sys/poll.h, setjmp/setjmp.h
	* sysdeps/arm/sys/ucontext.h, sysdeps/generic/sys/ucontext.h
	* sysdeps/i386/sys/ucontext.h, sysdeps/m68k/sys/ucontext.h
	* sysdeps/mach/hurd/i386/bits/sigcontext.h
	* sysdeps/mips/sys/ucontext.h, sysdeps/powerpc/novmxsetjmp.h
	* sysdeps/pthread/bits/sigthread.h
	* sysdeps/unix/sysv/linux/hppa/sys/ucontext.h
	* sysdeps/unix/sysv/linux/m68k/sys/ucontext.h
	* sysdeps/unix/sysv/linux/mips/sys/ucontext.h
	* sysdeps/unix/sysv/linux/nios2/sys/ucontext.h
	* sysdeps/unix/sysv/linux/powerpc/sys/ucontext.h
	* sysdeps/unix/sysv/linux/s390/sys/ucontext.h
	* sysdeps/unix/sysv/linux/sh/sys/ucontext.h
	* sysdeps/unix/sysv/linux/sparc/sys/ucontext.h
	* sysdeps/unix/sysv/linux/tile/sys/ucontext.h
	* sysdeps/unix/sysv/linux/x86/sys/ucontext.h:
	Use bits/types/__sigset_t.h.

	* misc/sys/select.h, posix/spawn.h
	* sysdeps/unix/sysv/linux/powerpc/sys/ucontext.h
	* sysdeps/unix/sysv/linux/sys/epoll.h
	* sysdeps/unix/sysv/linux/sys/signalfd.h:
	Use bits/types/sigset_t.h.

	* resolv/netdb.h, rt/mqueue.h: Use bits/types/sigevent_t.h.
	* rt/aio.h: Use bits/types/sigevent_t.h and bits/sigevent-consts.h.
	* socket/sys/socket.h: Don't include bits/sigset.h.

	* login/utmp_file.c, shadow/lckpwdf.c, signal/sigandset.c
	* signal/sigisempty.c, stdlib/abort.c, sysdeps/posix/profil.c
	* sysdeps/posix/sigignore.c, sysdeps/posix/sigintr.c
	* sysdeps/posix/signal.c, sysdeps/posix/sigset.c
	* sysdeps/posix/sprofil.c, sysdeps/posix/sysv_signal.c
	* sysdeps/unix/sysv/linux/nptl-signals.h:
	Include sigsetops.h.

	* signal/sigaddset.c, signal/sigandset.c, signal/sigdelset.c
	* signal/sigorset.c, stdlib/abort.c, sysdeps/posix/sigignore.c
	* sysdeps/posix/signal.c, sysdeps/posix/sigset.c:
	__sigaddset, __sigandset, __sigdelset, __sigemptyset, __sigorset
	now return no value.

	* signal/sigaddset.c, signal/sigdelset.c, signal/sigismem.c
	Include <errno.h>, <signal.h>, and <sigsetops.h> instead of
	"sigsetops.h".

	* signal/sigsetops.c: Explicitly define __sigismember,
	__sigaddset, and __sigdelset as compatibility symbols.

	* signal/Versions: Correct commentary on __sigpause,
	__sigaddset, __sigdelset, __sigismember.

	* inet/rcmd.c: Include sigsetops.h.  Convert old code using
	__sigblock/__sigsetmask to use __sigprocmask and friends.