Implement the svn:externals parser in JavaHL.

* subversion/bindings/javahl/native/jniwrapper/jni_list.hpp
  (Java::BaseMutableList, Java::MutableList): New base class and template.
  (Java::BaseList::size_type): Remove typedef.
  (Java::BaseList::length): Change to return a jint.
  (Java::BaseList::operator[]): Change index type to jint.
  (Java::List::operator[]): Likewise.
* subversion/bindings/javahl/native/jniwrapper/jni_list.cpp
  (Java::BaseMutableList): Implement.
  (BaseList::convert_to_vector): Adjust index type.

* subversion/bindings/javahl/native/org_apache_subversion_javahl_util_PropLib.cpp
  (Java_org_apache_subversion_javahl_util_PropLib_parseExternals):
   Finish implementation.
  (Java_org_apache_subversion_javahl_util_PropLib_unparseExternals):
   Update index type.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1539213 13f79535-47bb-0310-9956-ffa450edef68