Fix a valgrind warning: memcpy does not allow its arguments to overlap.

  /*

    We only need to check that stmt->field_count - if it is not null

    stmt->bind was initialized in mysql_stmt_prepare

    stmt->bind overlaps with bind if mysql_stmt_bind_param

    is called from mysql_stmt_store_result.

  */

  if (stmt->bind != bind)

    memcpy((char*) stmt->bind, (char*) bind, sizeof(MYSQL_BIND) * bind_count);

  for (param= stmt->bind, end= param + bind_count, field= stmt->fields ;