Fix diff for examples/xx_arealights/helpers.sh to avoid " error C7528: OpenGL reserves names containing '__' ".

helpers.sh.diff

164c164
< vec3 FetchDiffuseFilteredTexture(sampler2D texLightFiltered, vec3 _p1, vec3 _p2, vec3 _p3, vec3 _p4)
---
> vec3 FetchDiffuseFilteredTexture(sampler2D texLightFiltered, vec3 p1_, vec3 p2_, vec3 p3_, vec3 p4_)
167,168c167,168
<     vec3 V1 = _p2 - _p1;
<     vec3 V2 = _p4 - _p1;
---
>     vec3 V1 = p2_ - p1_;
>     vec3 V2 = p4_ - p1_;
171c171
<     float planeDistxPlaneArea = dot(planeOrtho, _p1);
---
>     float planeDistxPlaneArea = dot(planeOrtho, p1_);
173c173
<     vec3 P = planeDistxPlaneArea * planeOrtho / planeAreaSquared - _p1;
---
>     vec3 P = planeDistxPlaneArea * planeOrtho / planeAreaSquared - p1_;