Fix libedit detection on *BSD OS's
Fix libedit detection on *BSD OS's

The following patch allows the autoconf script to detect the presence of
libedit when there isn't a pkg-config file present and thus allowing
Varnish to detect libedit on OpenBSD/FreeBSD/NetBSD/DragonFly.

Fixes: #1003

ssm/pkg-varnish,ssm/pkg-varnish,ssm/pkg-varnish,ssm/pkg-varnish,ssm/pkg-varnish