RFR: JDK-8200083: Bump bootjdk requirement for JDK 11 to JDK 10

[Tim Bell]

Erik:
> I'm re-starting this review with the original proposed patch. This
> changes the required boot-JDK in configure from the set "9 10 or 11" to
> "10 or 11". It also changes what Oracle uses in its automated build
> environment setup from 9 GA to 10 GA.
>
> I do this based on the proposal [1] to retain the historical N - 1
> boot-JDK policy, which has not met any objections yet.
>
> http://cr.openjdk.java.net/~erikj/8200083/webrev.01/
>
> /Erik
>
> [1] http://mail.openjdk.java.net/pipermail/jdk-dev/2018-April/001075.html

Looks good.

Tim