Very minor speed-up in countevals

[juliamath]

Very minor speed-up in countevals

[stevengj]

Actually, I think LLVM already does this for you. Since n is a compile-time constant, its constant-folding optimizations eliminate all of the arithmetic:

julia> g = HCubature.GenzMalik(Val{3});

julia> @code_llvm HCubature.countevals(g)

define i64 @julia_countevals_60874(i8** dereferenceable(80)) #0 !dbg !5 {
top:
  ret i64 33
}

[giordano]

Good! Actually, I did see an improvement when benchmarking the two implementations (well, with my patch runtime of countevals went from ~1 ns to ~0.01 ns), so I thought that there was no optimization in place in current implementation. My bad for not having checked llvm code.