Review request for JDK-8135251: Use Unsafe.defineAnonymousClass for loading Nashorn script code

[Attila Szegedi]

Please review the revised changes for JDK-8135251 "Use Unsafe.defineAnonymousClass for loading Nashorn script code” <https://bugs.openjdk.java.net/browse/JDK-8135251>

The revision incorporates the following changes:
- the feature can be disabled by setting the "nashorn.disableVmAnonymousClasses system property”
- jdk9 root-level modules.xml explicitly exports sun.misc to jdk.scripting.nashorn
- the changes to the CodeInstaller and Compiler API have since been separately committed, so they are no longer part of this issue, making its surface area smaller.

Webrevs are found at:
http://cr.openjdk.java.net/~attila/8135251/webrev.jdk9 <http://cr.openjdk.java.net/~attila/8135251/webrev.jdk9>
http://cr.openjdk.java.net/~attila/8135251/webrev.jdk9-nashorn <http://cr.openjdk.java.net/~attila/8135251/webrev.jdk9-nashorn>

The fist webrev is for jdk9/modules.xml; the change simply adds an export of sun.misc to jdk.scripting.nashorn; it is also the reason why I included build-dev on this review.
The second webrev is the changes to the Nashorn code.

Thanks,
  Attila.