libbb: code shrink: introduce and use [_]exit_SUCCESS()

function                                             old     new   delta
exit_SUCCESS                                           -       7      +7
_exit_SUCCESS                                          -       7      +7
run_pipe                                            1562    1567      +5
pseudo_exec_argv                                     399     400      +1
finish                                                86      87      +1
start_stop_daemon_main                              1109    1107      -2
shutdown_on_signal                                    38      36      -2
runsv_main                                          1662    1660      -2
redirect                                            1070    1068      -2
read_line                                             79      77      -2
pause_and_low_level_reboot                            54      52      -2
list_i2c_busses_and_exit                             483     481      -2
less_exit                                             12      10      -2
identify                                            4123    4121      -2
grep_file                                           1161    1159      -2
getty_main                                          1519    1517      -2
fsck_minix_main                                     2681    2679      -2
free_session                                         132     130      -2
fdisk_main                                          4739    4737      -2
clean_up_and_exit                                     53      51      -2
bsd_select                                          1566    1564      -2
bb_daemonize_or_rexec                                198     196      -2
------------------------------------------------------------------------------
(add/remove: 2/0 grow/shrink: 3/17 up/down: 21/-34)           Total: -13 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/init/init.c b/init/init.c
index efab5dc..785a3b4 100644
--- a/init/init.c
+++ b/init/init.c
@@ -744,7 +744,7 @@
 	pid = vfork();
 	if (pid == 0) { /* child */
 		reboot(magic);
-		_exit(EXIT_SUCCESS);
+		_exit_SUCCESS();
 	}
 	/* Used to have "while (1) sleep(1)" here.
 	 * However, in containers reboot() call is ignored, and with that loop
@@ -752,7 +752,7 @@
 	 */
 	waitpid(pid, NULL, 0);
 	sleep1(); /* paranoia */
-	_exit(EXIT_SUCCESS);
+	_exit_SUCCESS();
 }
 
 static void run_shutdown_and_kill_processes(void)
@@ -942,7 +942,7 @@
 			for (a = G.init_action_list; a; a = a->next)
 				if (a->action_type == 0 && a->pid != 0)
 					kill(a->pid, SIGKILL);
-			_exit(EXIT_SUCCESS);
+			_exit_SUCCESS();
 		}
 	}
 #endif