* src/userdel.c, src/lastlog.c, src/gpasswd.c, src/newusers.c,

	* src/userdel.c, src/lastlog.c, src/gpasswd.c, src/newusers.c,
	src/chpasswd.c, src/groupmems.c, src/usermod.c, src/chgpasswd.c,
	src/vipw.c, src/su.c, src/useradd.c, src/groupmod.c, src/passwd.c,
	src/groupadd.c, src/chage.c, src/faillog.c, src/chsh.c: Use
	booleans for tests.
	* src/userdel.c, src/gpasswd.c, src/groupmems.c, src/usermod.c,
	src/groupmod.c, src/passwd.c: Use a break even after usage().