Unroll main compression loop even for FSE_MAX_TABLELOG>12

Loop unrolling still have some meaning even for FSE_MAX_TABLELOG>12 - it fetches nbBitsOut2 earlier and removes 3 ariops - "dec ip; cmp ip,start; jxx"
Support FSE_MAX_TABLELOG up to 25 and abort compilation otherwise
Fix
Merge pull request #1 from Bulat-Ziganshin/master

Bulat's patch on FSE_MAX_TABLELOG