(main): nohup now ignores the umask when creating nohup.out.

(main): nohup now ignores the umask when creating nohup.out.
nohup now closes stderr if it is a terminal and stdout is closed.
Be a little more paranoid about return values;
e.g., check for any negative return from open.
Assume free (NULL) works.
Close file descriptor leak when redirecting standard output to a file.