Add any ability to set EFL_SERVER_ONLY before the CBaseEntity::PostConstructor method is called.

[IVogel]

This particular flag (EFL_SERVER_ONLY) can't be set in any other way. It is useful when I want an entity that exists only on the server and does not occupy networked edicts.

I'm writing this in response to a more complex problem with triggers, where a brush-type entity won't call Touch if it has more complex geometry than a cube and has SOLID_VPHYSICS instead of SOLID_BBOX, since SOLID_BSP is not usable in this context. Hence, I'm resorting to using anim-type entities to make triggers with complex shapes. But they are occupying edicts.