icosphere primitive has incorrect triangle winding order

[tgfrerer]

compared to all other primitives, icosphere has the reverse triangle winding order, leading to the opposite face being culled when using back/front face culling.

[tgfrerer]

i have checked the other primitives, too - and #2259 fixes ofCone, which previously had a winding order glitch.

[arturoc]

@NickHardeman can you take a look?