Javadoc in 9 seems to treat all interfaces with only one method as functional interfaces

[Florian Weimer]

* Paul Benedict:

> It's a bug because it was an early decision in JDK 8 that got changed:
> http://mail.openjdk.java.net/pipermail/lambda-libs-spec-experts/2013-November/002379.html
>
> And then the change:
> http://mail.openjdk.java.net/pipermail/core-libs-dev/2014-January/024165.html

So it's a functional interface, but the documentation doesn't say so
because we don't want it to be a functional interface?  That's rather
odd and suggests that something went wrong with the design. :-)