Fix cos mistakenly running as acos

[JavidPack]

There is a typo that causes cos to run acos code. I believe this only affects preshaders, but I'm not too familiar with how things all work. (I did notice that cos would work correctly if the inputs involved other shader parameters)

https://github.com/icculus/mojoshader/blob/6148aaa1b4a9069c426a66cc028287d189e122ac/mojoshader_internal.h#L52-L57

Here is a shader that shows the bug

float4 PixelShaderFunction(float2 coords : TEXCOORD0) : COLOR0
{
    float4 color = tex2D(uImage0, coords);
    color.a = 1;
    float xPos = (coords.x - uSourceRect.x / uImageSize0.x) * (uImageSize0.x / uSourceRect.z);

    if(xPos > 0.5)
    {
        color.rgb = cos(uTime) * 0.5 + 0.5; 
    }
    else
    {
        color.rgb = sin(uTime) * 0.5 + 0.5; 
    }
}

https://github.com/icculus/mojoshader/assets/4522492/9a068130-a63f-4f79-bbcb-95fe4c1dd1e3

As shown above, the right side, the cos side, jumps between values as acos would.

Here is the fixed code running the same shader:

https://github.com/icculus/mojoshader/assets/4522492/8a517ccb-34c4-4f4a-acce-761b819e1516

Both cos and sin now smoothly interpolate, as expected.

[flibitijibibo]

Covered by #62, weird coincidence!