How do I use `__rvalue` expression on a struct property?

[Walter Bright]

Postblits and rvalue references do not mix.

Move constructors and rvalue references are a replacement for postblits. We 
didn't make any effort to reconcile the two.

If you're going to use move constructors and rvalue references, just delete the 
postblit code from the struct hierarchy.

Postblits are now an obsolete feature, left for legacy code.