[stunnel-users] Moving binaries to /usr/bin

The Debian package of stunnel changed the default location of the binaries, from /usr/sbin to /usr/bin. This is because we consider that stunnel is not an admin only tool, but is useful to regular users (as it does not require root privileges for several common use cases).

Please consider making this change. I provide no patch for this, because the one we use in Debian is heavily intertwined with other Debian-specific changes and is thus not useful for the main distribution.