Fix bad nice delay slot detection

I had seen code for using IS_VFPU to ignore OUT_RT etc., and was thinking that was a great idea for VT/etc., but I clearly didn't think about it properly.  There are IS_VFPU instructions that read/write GPRs, of course.

This should fix #3652.

Also treats VFPU delay slot niceness just like FPU: only exclude instructions that write to the CC flags.

-[Unknown]