RFR: 8153213: Jar manifest attribute "Multi-Release" accepts any value

[Steve Drach]

I’ve put up a new webrev that addresses the issue of having spaces before (and after) the value “true” in the Multi-Release attribute.

> Hi,
> Please review this simple fix to require that the jar manifest Multi-Release attribute has a value of “true" in order to be effective, i.e. to assert the jar is a multi-release jar.
> issue: https://bugs.openjdk.java.net/browse/JDK-8153213 <https://bugs.openjdk.java.net/browse/JDK-8153213>
> webrev: http://cr.openjdk.java.net/~sdrach/8153213/webrev/index.html <http://cr.openjdk.java.net/~sdrach/8153213/webrev/index.html>
> Thanks
> Steve