Handle malformed lines in hushlogins file.

Handle malformed lines in hushlogins file.

If a line in hushlogins file, e.g. /etc/hushlogins, starts with
'\0', then current code performs an out of boundary write.
If the line lacks a newline at the end, then another character is
overridden.

With strcspn both cases are solved.

Signed-off-by: Tobias Stoeckmann <tobias@stoeckmann.org>