*: use _exit() in sighandlers; showkey: do not use exit-thru-sighandler

While at it, make ESC sequences more readable; and removed check for
isatty(stdin) in reset. Code shrink:

   text    data     bss     dec     hex filename
 884771     936   17216  902923   dc70b busybox_old
 884723     936   17216  902875   dc6db busybox_unstripped

Signed-off-by: Marek Polacek <mmpolacek@gmail.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/miscutils/watchdog.c b/miscutils/watchdog.c
index 36902a2..6307826 100644
--- a/miscutils/watchdog.c
+++ b/miscutils/watchdog.c
@@ -24,7 +24,7 @@
 	write(3, &V, 1);  /* Magic, see watchdog-api.txt in kernel */
 	if (ENABLE_FEATURE_CLEAN_UP)
 		close(3);
-	exit(EXIT_SUCCESS);
+	_exit(EXIT_SUCCESS);
 }
 
 int watchdog_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;