On the fsfs-format7 branch:  Switch the remainder of the code from using
string txn IDs to structs.  This is again a large but simple patch.  The
only significant change change happens in tree.c where we add a txn ID
struct member to the fs_txn_root_data_t struct to be able to map incomming
API calls to the right txn ID without the need to parse it.

This is the last patch in the "numerical IDs" patch series.  A few smaller
follow-ups to the test code may be done in the couple of next days, tough.

* subversion/libsvn_fs_fs/dag.h
  (svn_fs_fs__dag_txn_root,
   svn_fs_fs__dag_clone_root,
   svn_fs_fs__dag_set_entry,
   svn_fs_fs__dag_clone_child,
   svn_fs_fs__dag_delete,
   svn_fs_fs__dag_make_dir, 
   svn_fs_fs__dag_make_file,
   svn_fs_fs__dag_copy): switch txn_id parameter type to struct

* subversion/libsvn_fs_fs/dag.c
  (set_entry,
   make_entry,
   svn_fs_fs__dag_set_entry,
   svn_fs_fs__dag_txn_root,
   svn_fs_fs__dag_txn_base_root,
   svn_fs_fs__dag_clone_child,
   svn_fs_fs__dag_clone_root,
   svn_fs_fs__dag_delete,
   svn_fs_fs__dag_make_file,
   svn_fs_fs__dag_make_dir,
   svn_fs_fs__dag_copy): signature change only

* subversion/libsvn_fs_fs/transaction.h
  (svn_fs_fs__txn_changes_fetch,
   svn_fs_fs__get_txn,
   svn_fs_fs__reserve_copy_id,
   svn_fs_fs__create_node,
   svn_fs_fs__set_entry,
   svn_fs_fs__add_change,
   svn_fs_fs__create_successor,
   svn_fs_fs__get_txn_ids): switch txn_id parameter type to struct

* subversion/libsvn_fs_fs/transaction.c
  (get_txn_proplist,
   write_final_changed_path_info,
   verify_locks): update callers
  (svn_fs_fs__txn_changes_fetch,
   svn_fs_fs__get_txn,
   svn_fs_fs__reserve_copy_id,
   svn_fs_fs__create_node,
   svn_fs_fs__set_entry, 
   svn_fs_fs__add_change,
   svn_fs_fs__create_successor,
   svn_fs_fs__open_txn,
   svn_fs_fs__get_txn_id): update signature; simplify 

* subversion/libsvn_fs_fs/tree.c
  (fs_txn_root_data_t): add txn_id member
  (make_txn_root): update signature
  (svn_fs_fs__txn_root): update caller
  (root_txn_id): new utility function
  (root_node,
   mutable_root_node,
   get_copy_inheritance, 
   make_path_mutable,
   fs_change_node_prop,
   merge_changes): update caller
  (add_change,
   merge): update signature
  (fs_make_dir,
   fs_delete_node,
   copy_helper,
   fs_make_file,
   apply_textdelta,
   apply_text,
   fs_paths_changed): update caller
  (make_txn_root): update signature and implementation

git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/fsfs-format7@1454959 13f79535-47bb-0310-9956-ffa450edef68