Move sigwait(3) from libpthread to libc

POSIX wants it in libc, that's where the function can be found on other
systems. Reported by naddy@, input from naddy@ and guenther@.
"looks ok" guenther@, ok deraadt@

Note: riding the libc/libpthread major cranks earlier today.

lib/libc/Symbols.list

···
 sigpending
 sigprocmask
 sigsuspend
+sigwait
 socket
 socketpair
 stat

lib/libc/gen/Makefile.inc

···
-#	$OpenBSD: Makefile.inc,v 1.79 2018/10/30 16:28:42 guenther Exp $
+#	$OpenBSD: Makefile.inc,v 1.80 2019/01/12 00:16:03 jca Exp $
 
 # gen sources
 .PATH: ${LIBCSRCDIR}/arch/${MACHINE_CPU}/gen ${LIBCSRCDIR}/gen
···
         rewinddir.c scandir.c seekdir.c setdomainname.c sethostname.c \
         setprogname.c setmode.c setproctitle.c shm_open.c \
         siginterrupt.c siglist.c signal.c signame.c \
-        sigsetops.c sleep.c statvfs.c strtofflags.c sysconf.c \
+        sigsetops.c sigwait.c sleep.c statvfs.c strtofflags.c sysconf.c \
         syslog.c syslog_r.c telldir.c time.c times.c \
         timespec_get.c tolower_.c tree.c ttyname.c \
         ttyslot.c toupper_.c ualarm.c uname.c unvis.c usleep.c \
···
 	psignal.3 pw_dup.3 pwcache.3 raise.3 readpassphrase.3 \
 	scandir.3 setjmp.3 setmode.3 setproctitle.3 shm_open.3 \
 	siginterrupt.3 signal.3 \
-	sigaddset.3 sleep.3 statvfs.3 sysconf.3 strtofflags.3 \
+	sigaddset.3 sigwait.3 sleep.3 statvfs.3 sysconf.3 strtofflags.3 \
 	syslog.3 time.3 times.3 timespec_get.3 toascii.3 tolower.3 toupper.3 \
 	ttyname.3 ualarm.3 uname.3 unvis.3 usleep.3 utime.3 valloc.3 vis.3

lib/libc/hidden/signal.h

···
-/*	$OpenBSD: signal.h,v 1.14 2016/09/26 05:57:58 guenther Exp $	*/
+/*	$OpenBSD: signal.h,v 1.15 2019/01/12 00:16:03 jca Exp $	*/
 /*
  * Copyright (c) 2015 Philip Guenther <[e-mail]>
  *
···
 PROTO_DEPRECATED(sigsetmask);
 PROTO_CANCEL(sigsuspend);
 PROTO_DEPRECATED(sigvec);
+PROTO_DEPRECATED(sigwait);
 PROTO_NORMAL(thrkill);
 
 #endif	/* !_LIBC_SIGNAL_H */

lib/libpthread/man/Makefile.inc

···
-# $OpenBSD: Makefile.inc,v 1.36 2016/03/30 06:38:42 jmc Exp $
+# $OpenBSD: Makefile.inc,v 1.37 2019/01/12 00:16:03 jca Exp $
 # $FreeBSD: Makefile.inc,v 1.6 1999/08/28 00:03:02 peter Exp $
 
 # POSIX thread man files
···
 	sem_wait.3
 
 MAN+=	pthreads.3 \
-	sigwait.3 \
 	flockfile.3 \
 	getc_unlocked.3 \
 	putc_unlocked.3

lib/libpthread/man/sigwait.3 lib/libc/gen/sigwait.3

···
-.\" $OpenBSD: sigwait.3,v 1.15 2013/06/05 03:44:50 tedu Exp $
+.\" $OpenBSD: sigwait.3,v 1.1 2019/01/12 00:16:03 jca Exp $
 .\"
 .\" David Leonard <[e-mail]>, 1998. Public domain.
-.Dd $Mdocdate: June 5 2013 $
+.Dd $Mdocdate: January 12 2019 $
 .Dt SIGWAIT 3
 .Os
 .Sh NAME
···
 Which thread returns from
 .Fn sigwait
 if more than a single thread is waiting is unspecified.
-.Pp
-.Sy Note :
-Code using the
-.Fn sigwait
-function must be compiled and linked with the
-.Cm -pthread
-option to
-.Xr gcc 1 .
 .Sh RETURN VALUES
 Upon successful completion,
 .Fn sigwait
···
 .Xr sigaction 2 ,
 .Xr sigpending 2 ,
 .Xr sigsuspend 2 ,
-.Xr pause 3 ,
-.Xr pthread_sigmask 3 ,
-.Xr pthreads 3
+.Xr pause 3
 .Sh STANDARDS
 .Fn sigwait
 conforms to

lib/librthread/Makefile

···
-#	$OpenBSD: Makefile,v 1.53 2018/10/21 17:07:24 visa Exp $
+#	$OpenBSD: Makefile,v 1.54 2019/01/12 00:16:03 jca Exp $
 
 LIB=pthread
 LIBCSRCDIR=	${.CURDIR}/../libc
···
 	rthread_rwlock.c \
 	rthread_rwlockattr.c \
 	rthread_sched.c \
-	rthread_sig.c \
 	rthread_stack.c \
 	rthread_spin_lock.c \
 	sched_prio.c

lib/librthread/Symbols.map

···
 		sem_trywait;
 		sem_unlink;
 		sem_wait;
-		sigwait;
 
 		/* used for debugging & regress */
 		_thread_dump_info;

lib/librthread/rthread_sig.c lib/libc/gen/sigwait.c

···
-/*	$OpenBSD: rthread_sig.c,v 1.18 2016/05/07 19:05:22 guenther Exp $ */
+/*	$OpenBSD: sigwait.c,v 1.1 2019/01/12 00:16:03 jca Exp $ */
 /*
  * Copyright (c) 2005 Ted Unangst <[e-mail]>
  * All Rights Reserved.
···
 
 #include <pthread.h>
 
-#include "rthread.h"
+#include "thread/rthread.h"
 #include "cancel.h"		/* in libc/include */
 
 int