Add OD_DIV_ROUND macro.
Add OD_DIV_ROUND macro.

This does branchless integer division with rounding, so you don't
 have to think about it.

ekr/daala,kbara/daala,kustom666/daala,nvoron23/daala,ascent12/daala,felipebetancur/daala,tdaede/daala_awcy_runs,kodabb/daala,KyleSiefring/daala,xiph/daala,felipebetancur/daala,HeadhunterXamd/daala,kodabb/daala,iankronquist/daala,ycho/daala,ycho/daala,mbebenita/daala,luctrudeau/daala,fluffy/daala,xiphmont/daala,tdaede/daala,kustom666/daala,felipebetancur/daala,KyleSiefring/daala,HeadhunterXamd/daala,xiphmont/daala,ekr/daala,kustom666/daala,felipebetancur/daala,luctrudeau/daala,nvoron23/daala,kodabb/daala,tribouille/daala,mbebenita/daala,kbara/daala,luctrudeau/daala,smarter/daala,ycho/daala,vr000m/daala,HeadhunterXamd/daala,KyleSiefring/daala,tdaede/daala,KyleSiefring/daala,xiph/daala,vr000m/daala,mbebenita/daala,kustom666/daala,mbebenita/daala,tribouille/daala,ycho/daala,ascent12/daala,tribouille/daala,kodabb/daala,tribouille/daala,metajack/daala,metajack/daala,smarter/daala,tribouille/daala,fluffy/daala,iankronquist/daala,ascent12/daala,kodabb/daala,xiph/daala,tdaede/daala_awcy_runs,ascent12/daala,iankronquist/daala,tdaede/daala,jmvalin/daala,smarter/daala,ycho/daala,luctrudeau/daala,kbara/daala,vr000m/daala,xiphmont/daala,tdaede/daala_awcy_runs,fluffy/daala,HeadhunterXamd/daala,xiph/daala,xiphmont/daala,kbara/daala,iankronquist/daala,xiph/daala,xiphmont/daala,jmvalin/daala,kustom666/daala,nvoron23/daala,metajack/daala,jmvalin/daala,HeadhunterXamd/daala,ekr/daala,ascent12/daala,vr000m/daala,luctrudeau/daala,jmvalin/daala,mbebenita/daala,felipebetancur/daala,nvoron23/daala,smarter/daala,jmvalin/daala,vr000m/daala,nvoron23/daala,KyleSiefring/daala,tdaede/daala_awcy_runs,iankronquist/daala,tdaede/daala