v8.0 is available.

- Improved speed by about 50-60%. Up to 7 CPD on 290X.
- Improved chain targeting: more 8-10 chains and less 4-6 chains.
- Added "-ss 3" option for very slow CPU.
- Removed "-hc" option.
- Removed "-ss 0" option, works as "-ss 1" now.