Cabal config corrupted when using Unicode

```
$ git clone https://github.com/hvr/-.git 無
...
$ cd 無
$ runghc Setup.hs configure
Configuring 無-0...
$ runghc Setup.hs build
Setup.hs: Saved package config file header is corrupt. Try re-running the 'configure' command.
```
