big <utmp.h>-inspired netbsd switch

import/switch of:
init, getty, reboot, halt, shutdown, wall, last

changes:
	. change reboot() call to netbsd prototype and args
	. allows pristine <utmp.h>
	. use clean <sys/reboot.h> instead of <minix/reboot.h>
	. implement TIOCSCTTY for use by getty so getty can get
	  controlling terminal from init's child(ren)
	. allow NULL envp for exec

Change-Id: I5ca02cb4230857140c08794bbfeba7df982c58a3

libexec/Makefile

@@ -5,7 +5,8 @@
 
 SUBDIR= \
 	fingerd ftpd	\
-	ld.elf_so
+	ld.elf_so	\
+	getty
 
 .if defined(__MINIX)
 SUBDIR+= makewhatis