readdir() breaks when there are unicode filenames present (on Linux)

Before adding a unicode filename:

```
julia> readdir()
4-element String Array:
 "new\nline"
 "NGrep.jl" 
 "poem"     
 "sp ace"   
```

After:

```
julia> readdir()
5-element String Array:
 "☃"       
 ""        
 "ine"     
 "NGrep.jl"
 "poem"  
```

If it were correct, the second result would look like the first result, but with "☃" at the start of the array.
