Updates to a number of apps to remove warnings/compile errors under libc5.

Tested under both libc5 and libc6 and all seems well with these fixes.
 -Erik

poweroff.c

@@ -28,8 +28,8 @@ extern int poweroff_main(int argc, char **argv)
 {
 #ifdef BB_FEATURE_LINUXRC
 	/* don't assume init's pid == 1 */
-	exit(kill(*(findPidByName("init")), SIGUSR2));
+	return(kill(*(findPidByName("init")), SIGUSR2));
 #else
-	exit(kill(1, SIGUSR2));
+	return(kill(1, SIGUSR2));
 #endif
 }