RFR (S) 8218593: Symbol leak in prepend_host_package_name

[coleen.phillimore at oracle.com]

Summary: add appropriate refcounting for Symbols stomped by parsing

open webrev at http://cr.openjdk.java.net/~coleenp/2019/8218593.01/webrev
bug link https://bugs.openjdk.java.net/browse/JDK-8218593

Tested with runThese and verifying symboltable logging shows similar 
numbers of symbols unloaded.   Ran tests added for the change which 
added the function prepend_host_package_name().  Also ran tier1-3.

Thanks,
Coleen