Add support for cracking KDE KWallet files

Add support for cracking KDE KWallet files.

```
$ ../run/john -fo:kwallet -t # 2 *  Xeon E5620 
Benchmarking: KDE KWallet SHA-1 [32/64]... (8xOMP) DONE
Raw:	7245 c/s real, 1017 c/s virtual
```