Follow r329348 in ipcs for getting rid of the requirement to include SysV IPC headers with _KERNEL
This also fixes the build of platforms using gcc
https://ci.freebsd.org/job/FreeBSD-head-mips-build/477/console
00:05:45.272 In file included from /usr/src/usr.bin/ipcs/ipcs.c:52: 00:05:45.272 /usr/src/usr.bin/ipcs/ipc.h:71: warning: redundant redeclaration of 'seminfo' 00:05:45.272 /usr/obj/usr/src/mips.mips/tmp/usr/include/sys/sem.h:138: warning: previous declaration of 'seminfo' was here 00:05:45.272 /usr/src/usr.bin/ipcs/ipc.h:72: warning: redundant redeclaration of 'msginfo' 00:05:45.272 /usr/obj/usr/src/mips.mips/tmp/usr/include/sys/msg.h:171: warning: previous declaration of 'msginfo' was here 00:05:45.272 /usr/src/usr.bin/ipcs/ipc.h:73: warning: redundant redeclaration of 'shminfo' 00:05:45.272 /usr/obj/usr/src/mips.mips/tmp/usr/include/sys/shm.h:153: warning: previous declaration of 'shminfo' was here 00:05:45.278 *** [ipcs.o] Error code 1 00:05:45.278 00:05:45.278 make[4]: stopped in /usr/src/usr.bin/ipcs 00:05:45.278 1 error