Disallow moveToThread(this)

It's quite surprising that moveToThread(this) is actually allowed.

I have seen this used in a lot of real customer code. People do not understand that it's a crash waiting to happen - and one that's hard to debug even.

It's very un-Qt to allow something that's broken with no reason for it.

It's probably 6.0 material to completely disallow this. So at least a deprecation of the behaviour along with a warning would be good.