let Shell know namespace sepatator '\'

in a PHP_Shell, if i input 
````
Illuminate\Support\Str::ascii('abc')
```

output is
```
unknown tag: 384 (T_NS_SEPARATOR): \  
                                      
unknown tag: 384 (T_NS_SEPARATOR): \  
                                      
'abc'                                 
```

so i add 'T_NS_SEPARATOR'