Forces deterministic FP operations when online

[RipleyTom]

Turns out rcp sse instruction result differs between Intel and AMD.
From our spu float test with both set to accurate:

$ diff output_AMD.txt output_INTEL.txt 
33401,33402c33401,33402
< frest   ([04]) -> 3fe55500 3fe55500 3fe55500 3fe55500
< frest   ([05]) -> bfe55500 bfe55500 bfe55500 bfe55500
---
> frest   ([04]) -> 3fe55400 3fe55400 3fe55400 3fe55400
> frest   ([05]) -> bfe55400 bfe55400 bfe55400 bfe55400
33405,33406c33405,33406
< frest   ([08]) -> 3fe6dc00 3fe6dc00 3fe6dc00 3fe6dc00
< frest   ([09]) -> bfe6dc00 bfe6dc00 bfe6dc00 bfe6dc00
---
> frest   ([08]) -> 3fe6db00 3fe6db00 3fe6db00 3fe6db00
> frest   ([09]) -> bfe6db00 bfe6db00 bfe6db00 bfe6db00
33410,33413c33410,33413
< frest   ([13]) -> be7ad900 be7ad900 be7ad900 be7ad900
< frest   ([14]) -> 3e6ad900 3e6ad900 3e6ad900 3e6ad900
< frest   ([15]) -> bf0a3700 bf0a3700 bf0a3700 bf0a3700
< frest   ([16]) -> 3f0a3700 3f0a3700 3f0a3700 3f0a3700
---
> frest   ([13]) -> be7ad800 be7ad800 be7ad800 be7ad800
> frest   ([14]) -> 3e6ad800 3e6ad800 3e6ad800 3e6ad800
> frest   ([15]) -> bf0a3600 bf0a3600 bf0a3600 bf0a3600
> frest   ([16]) -> 3f0a3600 3f0a3600 3f0a3600 3f0a3600

This results in sync issues between AMD and INTEL users in multiplayer games.
Fixes #13599.
And probably #13449.

[RipleyTom]

I changed the approach to force deterministic results when config specifies online.