Implement many fs_fs routines related to beginning a transaction and reading/writing node-revisions in a transaction.
Implement many fs_fs routines related to beginning a transaction and
reading/writing node-revisions in a transaction.

   * subversion/libsvn_fs_fs/fs_fs.c
     (read_rep_offsets): Handle the extended representation format
       string that can contain the "this" identifier.
     (open_txn_node_rev): New, opens a node-revision file located in a
       transaction.
     (svn_fs__fs_get_node_revision): Handle node-revisions that may be
       located inside a transaction.
     (representation_string): New helper function that generates
       representation location strings.
     (write_noderev_txn): New helper function that writes out a
       node-revision.
     (svn_fs__fs_put_node_revision): Implemented.
     (create_new_txn_noderev_from_rev): New helper function that
       clones a node-rev from a revision into a transaction.
       Currently it is only used to clone the root-node.
     (svn_fs__fs_begin_txn): Implement.
     (get_txn_proplist): New helper function that returns the
       transaction property list.
     (svn_fs__fs_change_txn_prop, svn_fs__fs_get_txn): Implement.


git-svn-id: f8a4e5e023278da1e04e203c7fe051e3c4285d88@849516 13f79535-47bb-0310-9956-ffa450edef68

wbond/subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,wbond/subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,wbond/subversion,wbond/subversion,wbond/subversion,wbond/subversion,YueLinHo/Subversion,wbond/subversion