Avoid the tinny audio pause while using rewind

[[Unknown]]

So, I'm using a 3770 3.4Ghz, GTX 950, and 16GB of RAM on Windows 7 64-bit SP1. So not all that different from your specs.

I set the frequency to every frame, and it spent 24% of its time dealing with savestates. This is probably why there's sometimes pauses. A lot of that time is just spent on memory access - but I do see an opportunity to offload some work onto another thread. Let's see if it helps...

-[Unknown]