libxvid additions and clarification

[Selur]

Trying to leave xvid_encraw and mencoder behind for Xvid encoding I compared FFmpegs libxvid options against mencoder.

There are a few options which are unclear if I mapped them correctly and there seem to be a bunch of options missing.

I have no clue how to properly map:

1. turbo (missing?)
2. zones (missing?)
3. me_quality since me_method only seems to have 5 instead of 7 options
4. cartoon (missing?)
5. chroma_opt (missing?)
6. vhq since mdb only has 3 instead of 5 options
7. keyframe_boost (missing?)
8. kfthreshold (missing?)
9. kfreduction (missing?)
10. bf_threshold (missing?)
11. packed (missing?)
12. curve_compression_high
13. curve_compression_low
14. overflow_control_strength
15. max_overflow_improvement
16. max_overflow_degradation
17. bvhq (missing?)
18. vbv_initial (missing?)

see:
​https://docs.google.com/spreadsheets/d/1m6MlYd5lLck0fcnMmJD6taAfFQLC4YFZjITUMe11UbI/edit?usp=sharing

Would be nice if:

1. someone could tell me how to properly map those options to ffmpeg for Xvid encoding
2. if missing options could be added to ffmpegs libxvid support.