GPU/Math3D: Add component swizzlers for Vec2, Vec3 and Vec4.
GPU/Math3D: Rename VecXRef::Mul to the star operator.
GPU/Math3D: Support converting Vec3 and Vec4 objects to u32 color values.
GPU/Math3D: Add methods for casting vectors.
GPU/Math3D: Replace VecX::Lerp methods with more general and clearer Lerp and LerpInt template functions.