Ignore unreasonable timestep values.

This fixes #5202 (Crisis Core stuttering) and improves Mana Khemia's "Who are you?" sound effect while loading savedata.  May also improve Monster Hunter's similar issue.

This basically ignores (for sleeping purposes, etc.) sub-10 fps, which can happen if a game is not rendering new frames for a period of time.

There's now some stutter in Mana Khemia before "Who are you?", but then it plays that clearly.  Actually, I just checked my PSP, and now remember... it annoyingly plays "Who are you?" twice (I had repressed this.)  In PPSSPP, the first one is just a stutter (I suspect because savedata blazes by too quickly) and the second one is played clearly now.

-[Unknown]