Latest patch from vodz. Adds a check for divide by zero in the posix

math suport, cleaner math syntax error checking, moves redundant signal
string tables (from kill and ash) into libbb and provides a few
cleanups elsewhere.

update.c

@@ -69,9 +69,6 @@ extern int update_main(int argc, char **argv)
 	if (daemon(0, 1) < 0)
 		perror_msg_and_die("daemon");
 
-	/* Become a proper daemon */
-	setsid();
-	chdir("/");
 #ifdef OPEN_MAX
 	for (pid = 0; pid < OPEN_MAX; pid++) close(pid);
 #else