Log Message:
nb1: Put conf and pid files back where they belong after the 4.15 update.

(PKG_SYSCONFDIR already includes "stunnel" by default, so avoid the
package adding another and making $PREFIX/etc/stunnel/stunnel/stunnel.conf;
the pidfile does not normally belong under $PREFIX as $PREFIX/var/run is
not normally cleaned/checked by OS-supplied processes.)