On the fsx branch: Implement various tests for the svn_packed_data__* API.

* subversion/tests/libsvn_subr/packed-data-test.c
  (get_read_root): document
  (sub_record_t,
   base_record_t,
   SUB_RECORD_COUNT,
   BASE_RECORD_COUNT,
   sub_records,
   test_data): new test data
  (verify_uint_stream,
   verify_int_stream,
   pack_subs,
   pack,
   unpack_subs,
   unpack,
   compare_binary,
   compare_subs,
   compare): new utility functions
  (test_uint_stream,
   test_int_stream,
   test_byte_stream,
   test_empty_structure,
   test_full_structure): new test functions
  (test_funcs): register new tests


git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/fsx@1509228 13f79535-47bb-0310-9956-ffa450edef68