Don't declare union semun in userspace unless _WANT_SEMUN is defined.

POSIX explicitly states that the application must declare union semun.
This makes no sense, but it is what it is.  This brings us into line
with Linux, MacOS/Darwin, and NetBSD.

In a ports exp-run a moderate number of ports fail due to a lack of
approprate autotools-like discovery mechanisms or local patches.  A
commit to address them will follow shortly.

PR:		224300, 224443 (exp-run)
Reviewed by:	emaste, jhb, kib
Exp-run by:	antoine
Sponsored by:	DARPA, AFRL
Differential Revision:	https://reviews.freebsd.org/D14492

contrib/sendmail/include/sm/os/sm_os_freebsd.h

@@ -34,7 +34,7 @@
 # define SM_CONF_SHM	1
 #endif /* SM_CONF_SHM */
 #ifndef SM_CONF_SEM
-# define SM_CONF_SEM	1
+# define SM_CONF_SEM	2
 #endif /* SM_CONF_SEM */
 #ifndef SM_CONF_MSG
 # define SM_CONF_MSG	1

lib/libc/gen/semctl.c

@@ -34,6 +34,7 @@ __FBSDID("$FreeBSD$");
 #ifndef NO_COMPAT7
 #define _WANT_SEMUN_OLD
 #endif
+#define _WANT_SEMUN
 
 #include <sys/types.h>
 #include <sys/ipc.h>

lib/libc/sys/semctl.2

@@ -25,7 +25,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd September 12, 1995
+.Dd February 23, 2018
 .Dt SEMCTL 2
 .Os
 .Sh NAME
@@ -55,10 +55,7 @@ For the commands that use the
 .Fa arg
 argument,
 .Fa "union semun"
-is defined as follows:
-.\"
-.\" From <sys/sem.h>:
-.\"
+must be defined as follows:
 .Bd -literal
 union semun {
         int     val;            /* value for SETVAL */
@@ -66,6 +63,12 @@ union semun {
         u_short *array;         /* array for GETALL & SETALL */
 };
 .Ed
+Non-portable software may define
+.Dv _WANT_SEMUN
+before including
+.Pa sys/sem.h
+to use the system definition of
+.Fa "union semun" .
 .Pp
 Commands are performed as follows:
 .\"

sys/sys/param.h

@@ -60,7 +60,7 @@
  *		in the range 5 to 9.
  */
 #undef __FreeBSD_version
-#define __FreeBSD_version 1200058	/* Master, propagated to newvers */
+#define __FreeBSD_version 1200059	/* Master, propagated to newvers */
 
 /*
  * __FreeBSD_kernel__ indicates that this system uses the kernel of FreeBSD,

sys/sys/sem.h

@@ -76,6 +76,7 @@ union semun_old {
 };
 #endif
 
+#if defined(_KERNEL) || defined(_WANT_SEMUN)
 /*
  * semctl's arg parameter structure
  */
@@ -84,6 +85,7 @@ union semun {
 	struct		semid_ds *buf;	/* buffer for IPC_STAT & IPC_SET */
 	unsigned short	*array;		/* array for GETALL & SETALL */
 };
+#endif
 
 /*
  * commands for semctl

usr.bin/svn/lib/libapr/apr.h

@@ -261,7 +261,7 @@ extern "C" {
 #define APR_HAVE_STRSTR         1
 #define APR_HAVE_MEMCHR         1
 #define APR_HAVE_STRUCT_RLIMIT  1
-#define APR_HAVE_UNION_SEMUN    1
+#define APR_HAVE_UNION_SEMUN    0
 #define APR_HAVE_SCTP           1
 #define APR_HAVE_IOVEC          1