Prevent type mismatch warnings.

* tools/server-side/svnfsfs/load-index-cmd.c
  (parse_index_line): Use an intermediate variable of a fixed type and
                      then cast to the respective platform type.  We
                      can't test for value ranges here as there is no
                      suitable MAX constant for apr_off_t.  OTOH, this
                      is an expert tool and the user is ultimately
                      responsible for providing correct / valid data.

Found by: gbg

git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1596113 13f79535-47bb-0310-9956-ffa450edef68