Unit test on high bit shifts

The following tests might give different results depending on platforms:

```haxe
function shl( x, y ) return x << y;
shl(1,33); // can be 0 or 2, depending if native CPU opcode is used (which does &31 on shift value)
```

https://c9x.me/x86/html/file_module_x86_id_285.html

I think we should make it platform agnostic, but I'm curious to know if the issue is HL specific or if some other platforms are affected.