make a few struct bb_applet members conditional

rename sllep_and_die -> xfunc_die
make fflush_stdout_and_exit NOFORK-safe
fix some buglets found by randomconfig

coreutils/cmp.c

@@ -23,14 +23,14 @@
 
 #include "busybox.h"
 
-static FILE *cmp_xfopen_input(const char * const filename)
+static FILE *cmp_xfopen_input(const char *filename)
 {
 	FILE *fp;
 
 	fp = fopen_or_warn_stdin(filename);
 	if (fp)
 		return fp;
-	sleep_and_die();	/* We already output an error message. */
+	xfunc_die();	/* We already output an error message. */
 }
 
 static const char fmt_eof[] = "cmp: EOF on %s\n";

coreutils/echo.c

@@ -107,7 +107,9 @@ int bb_echo(char **argv)
 		putchar(' ');
 	}
 
+#if ENABLE_FEATURE_FANCY_ECHO
  newline_ret:
+#endif
 	if (nflag) {
 		putchar('\n');
 	}