Fix some unused variable warnings.
Fix some unused variable warnings.

One of these was a real (but harmless) mistake.
The others were only used in certain non-default configurations.
Control these with explicit, named #defines now.
Thanks to Sean Silva for the report.

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