RFR: 8219202: Use Unsynchronized StringBuilder in sun.net.www.ParseUtil

[Alan Malloy]

Hello. Please review this patch to use StringBuilder instead of
StringBuffer in sun.net.www.ParseUtil, a usage that does not need
synchronization.

bug: https://bugs.openjdk.java.net/browse/JDK-8219202
webrev: http://cr.openjdk.java.net/~cushon/8219202/webrev.01/

Testing: All of jtreg:test/jdk/sun/net/www pass locally. No new test added,
as no behavior change is intended.

Thanks,
   Alan