[theora] NHW Project - improvement of -l8 high compression setting

[Raphael Canut]

Hello,

For those interested, I have improved -l8 high compression quality
setting.This setting is now better, more precision.Files are also a little
smaller and I don't have touched the entropy coding schemes, so we can
still save 2KB per .nhw compressed file.

More at: http://nhwcodec.blogspot.com/

I am also working on -l9 quality setting, but it is not ready for now,
notably as x265 (HEVC) starts to excel at these very high compression
ratios... For the other compression ratios, I prefer the NHW Project! Your
opinion would be very welcome! Any help for very high compression is also
welcome!

Many thanks!
Cheers,
Raphael