[PATCH] add documentation about backend naming for VMOD authors

[Dridi Boukelmoune]

Sorry for the frenchism but it's turning into a "dialogue de sourd" :(

> VCC is not involved in dynamic backends.

I *know* that.

In the "Writing a director" documentation I *recommend* directors
writers to back their director with a *VMOD object* because VMOD
object come with a *unique* vcl_name and don't outlive the VCL's
lifespan. It makes VMOD objects in my opinion the best facility to
write a director.

My point is that a VMOD writer *should be responsible* for not
conflicting with other well-behaving VMODs. In this case, claiming a
unique vcl_name as a first level of namespace seems like a good idea
to me.

> As Geoff said, a VMOD can spit out as many backends as it wants...

I *know* that.

In vmod-named I use the object's vcl_name as a basis for the backend,
and use the resolved IP address to ensure uniqueness within this
namespace.

Crossing fingers that this time I'm making some sense.

Dridi