RFR(S): 8142329: [JVMCI] pass Handle by value

[Roland Schatz]

Hi,

In JVMCI we have a few methods using `Handle&` as argument, according to 
the comment in handle.hpp this should be `Handle` directly.

JIRA:
https://bugs.openjdk.java.net/browse/JDK-8142329

Webrev:
http://cr.openjdk.java.net/~rschatz/JDK-8142329/webrev.00/

Please review.

Thanks,
Roland