Revision 1649797

Simplify the r0 template in FSX.  Because we treat directories with NULL
text reps as empty (and do so efficiently), we can simply ommit the text
rep for the root directory in r0.  The remainder are simple strings that
we can take length info from and that can be composed into r0.

* subversion/libsvn_fs_x/fs_x.c
  (write_revision_zero):  Omit /@0 text rep and compose r0 from strings.
                          Derive offset info from string lengths.