Preshader bool outputs are not implemented

[tobil4sk]

While running a game (through proton and fna as the xna implementation), I noticed this assert was being triggered during preshader parsing:

mojoshader/mojoshader.c

Line 2791 in ad5dff8

assert(0 && "Unhandled fxlc.tokens[1] in parse_preshader!");

it seems case 5 is not implemented in this switch. I believe this corresponds to bool output operands:

https://gitlab.winehq.org/wine/wine/-/blob/490f6d5dcbb2a5047345b8af88d114bbcaad69a8/dlls/d3dx9_36/preshader.c#L416-L420

[flibitijibibo]

This is something the preshader VM also doesn't support - we just assume float registers for now:

https://github.com/icculus/mojoshader/blob/main/mojoshader_effects.c#L19

It's a pretty low priority on FNA's end since it's pretty easy for developers to pass /Op and skip the VM altogether.