readdlm / mmap_array test failure on 32-bit (linux)

```
        From worker 2:       * readdlm
exception on 2: ERROR: no method mmap_array(DataType,(Int64,),IOStream)
 in readdlm_auto at datafmt.jl:46
 in runtests at /home/jameson/julia/test/testdefs.jl:5
 in anonymous at multi.jl:767
 in run_work_thunk at multi.jl:501
 in anonymous at task.jl:767
at readdlm.jl:1
```
