Added uint64_cntbits().
Added uint64_cntbits().

fluffyfreak/bx,MikePopoloski/bx,bkaradzic/bx,BlueCrystalLabs/bx,coconutxin/bx,coconutxin/bx,attilaz/bx,septag/termite,fluffyfreak/bx,bkaradzic/bx,OlegOAndreev/bx,septag/termite,septag/bx,0-wiz-0/bx,dariomanesku/bx,septag/termite,ShuangxueBai/bx,pigpigyyy/bx,attilaz/bx,septag/termite,ShuangxueBai/bx,0-wiz-0/bx,pigpigyyy/bx,OlegOAndreev/bx,mmicko/bx,MikePopoloski/bx,septag/termite,septag/termite,BlueCrystalLabs/bx,dariomanesku/bx,septag/bx,u-engine/bx,mmicko/bx,u-engine/bx