Int64 loses type within the array.

Int64 loses its value within the array, which causes serious problems in an implementation like the one below.

https://github.com/barisyild/hxvm-lua/blob/116f62154c21b6dc9f6cebd51e21d32612fd2d80/src/vm/lua/Lua.hx#L190

```haxe
var args:Array = [];
args.push(haxe.Int64.parseString("9138745278763343734"));
args.push(0.24332);

if(args[0] != haxe.Int64.parseString("9138745278763343734"))
throw "Error: args[0] != 9138745278763343734 " + args[0];

trace("PASS!");
```
```ex
Error: args[1] != haxe.Int64.parseString("9138745278763343734") 9.13874527876334e+18
```