Avoid an underflow in the SSE mixers if BufferSize is less than 4
Avoid an underflow in the SSE mixers if BufferSize is less than 4

arkana-fts/openal-soft,alexxvk/openal-soft,irungentoo/openal-soft-tox,Wemersive/openal-soft,aaronmjacobs/openal-soft,BeamNG/openal-soft,alexxvk/openal-soft,franklixuefei/openal-soft,arkana-fts/openal-soft,Wemersive/openal-soft,mmozeiko/OpenAL-Soft,BeamNG/openal-soft,mmozeiko/OpenAL-Soft,aaronmjacobs/openal-soft,rryan/openal-soft,franklixuefei/openal-soft,rryan/openal-soft,irungentoo/openal-soft-tox