Update manpage: OpenSSL might also need /dev/urandom inside chroot

Update manpage: OpenSSL might also need /dev/urandom inside chroot

As reported in trac ticket #646, OpenSSL might also need /dev/urandom to
be available in the chroot.  This depends on OS, OS version and ssl library
configuration.  Update the manpage to better explain this.

Signed-off-by: Steffan Karger <steffan@karger.me>
Acked-by: Gert Doering <gert@greenie.muc.de>
Message-Id: <1452196364-18786-1-git-send-email-steffan@karger.me>
URL: http://article.gmane.org/gmane.network.openvpn.devel/10954
Signed-off-by: Gert Doering <gert@greenie.muc.de>