LadspaEffect: use stack for downsampling
Not likely to be an issue currently, but if(when) we at some point allow >44.1k samplerates for playback, we may run in a situation where we have to downsample audio for processing, and thus we'd be doing heap allocation every period - it's best to fix this in advance so we're using stack for it for now (may be replaced with memory management later though)
Merge pull request #1086 from diizy/master

LadspaEffect: use stack for downsampling