Fix some warnings

```
ReadKey.xs:1400:3: warning: expression result unused; should this cast be to 'void'? [-Wunused-value]
                (void*)hv_delete(filehash,(char*)&handle,sizeof(int),0);
                ^    ~
ReadKey.xs:1401:3: warning: expression result unused; should this cast be to 'void'? [-Wunused-value]
                (void*)hv_delete(modehash,(char*)&handle,sizeof(int),0);
                ^    ~
```