normalize method
Normalizes this.
Implementation
double normalize() {
final l = length;
if (l == 0.0) {
return 0.0;
}
final d = 1.0 / l;
_v4storage[0] *= d;
_v4storage[1] *= d;
_v4storage[2] *= d;
_v4storage[3] *= d;
return l;
}