On the 'move-tracking-2' branch: Parse the correct number of branch
instance data blocks.

* subversion/libsvn_delta/branching.c
  (svn_branch_family_parse): Read the number of branch instances.
  (svn_branch_revision_root_parse): Parse that number of instances.
  (svn_branch_family_serialize): Write the number of branch instances.

* subversion/libsvn_ra/ra_loader.c
  (default_repos_info): Update the initial metadata accordingly.

git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/move-tracking-2@1639616 13f79535-47bb-0310-9956-ffa450edef68