RFR: 8155770 Correct URLClassLoader API documentation to explicitly say jar-scheme URL's are accepted

[Steve Drach]

Hi,

Please review this simple change to the URLClassLoader specification.

issue: https://bugs.openjdk.java.net/browse/JDK-8155770 
<https://bugs.openjdk.java.net/browse/JDK-8155770>
webrev: http://cr.openjdk.java.net/~sdrach/8155770/webrev/ 
<http://cr.openjdk.java.net/~sdrach/8155770/webrev/>

Thanks,
Steve