RFR: 8231355: Remove unused utility methods in libjava

[Claes Redestad]

Hi,

please review this patch which removes unused methods and redundant
aliases from jni_util and friends in libjava.

There's one affected call site in the hotspot runtime code, otherwise
this is mainly a java.base-internal cleanup.

Bug:    https://bugs.openjdk.java.net/browse/JDK-8231355
Webrev: http://cr.openjdk.java.net/~redestad/8231355/open.00/

Testing: tier1+2

Thanks!

/Claes