Remove unused variable

Refs trac:4004

This commit was SVN r30021.

The following Trac tickets were found above:
  Ticket 4004 --> https://svn.open-mpi.org/trac/ompi/ticket/4004

test/datatype/ddt_raw.c

@@ -99,7 +99,6 @@ static int local_copy_ddt_raw( ompi_datatype_t* pdt, int count, int iov_num )
     opal_convertor_t* convertor;
     TIMER_DATA_TYPE start, end;
     long total_time;
-    int i;
     uint32_t iov_count = iov_num;
     size_t max_data = 0, remaining_length;