Region brush doesn't cull brush entities

[4LT]

This can cause unexpected behavior when a brush entity outside the region "points" to (e.g. via target field) a point entity that is also outside the region. An example of this occurred with my own mod where a brush entity must have a (non-world) target. If it does not, objerror is called. I can imagine this would cause some goofy behavior with func_train as well.