JIT: fix fsel/ps_sel implementations for NaN input

This works and passes my torture tests (bit-exact to interpreter algorithm),
but I have no idea why.

This fixes Beyond Good and Evil (at the least).

I don't feel 100% comfortable pushing this right now as I really don't get quite why it works. NLE really shouldn't be right. I tried to write a tester here: http://ideone.com/C4gzqw for some reason it shows the only working algorithm (matching the C one) as being the NLE one...