Second round of converting newstyle JavaHL native classes to cache all
method and field IDs; ths time it's classes outside of jniwrapper.

[in subversion/bindings/javahl]
* native/jniwrapper/jni_object.hpp (ClassCache):
   Declare new cached classes: external_item.
* native/jniwrapper/jni_class_cache.cpp (ClassCache::ClassCache):
   Init members and call static initializers for wrapped classes:
   JavaHL::ExternalItem.

* native/ExternalItem.hpp, native/ExternalItem.cpp:
   Convert to init static method and field IDs and use
   the cached class reference.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1544501 13f79535-47bb-0310-9956-ffa450edef68