Bit manipulations of floating point numbers and endianness

* `doubleToLongBits`/`longBitsToDouble`/`floatToIntBits`/`intBitsToFloat`
* `Double.hashCode` and `Float.hashCode`
* `ByteOrder.nativeOrder()`
Hum ... What about at the definition of `numberHashCode` instead? Since the same comment applies when calling `numberHashCode` from `scalajsenv.js`.