sub method
Subtracts arg
from this.
Implementation
void sub(Quaternion arg) {
final argStorage = arg._qStorage;
_qStorage[0] = _qStorage[0] - argStorage[0];
_qStorage[1] = _qStorage[1] - argStorage[1];
_qStorage[2] = _qStorage[2] - argStorage[2];
_qStorage[3] = _qStorage[3] - argStorage[3];
}