Revision 1506576

On the fsfs-improvements branch:  With the new ID types in place,
we can now replace other string with a struct

* subversion/libsvn_fs_fs/fs.h
  (representation_t): replace the uniquifier string by a proper struct

* subversion/libsvn_fs_fs/fs_fs.c
  (svn_fs_fs__noderev_same_rep_key,
   svn_fs_fs__rep_copy): simplify as uniquifiers can now simply memory blocks

* subversion/libsvn_fs_fs/low_level.c
  (svn_fs_fs__parse_representation,
   svn_fs_fs__unparse_representation): update parser and writer

* subversion/libsvn_fs_fs/temp_serializer.c
  (serialize_representation,
   deserialize_representation): embedded structs don't need a special handling

* subversion/libsvn_fs_fs/transaction.c
  (set_uniquifier): update / simplify