add method
Add o to this.
Implementation
void add(Matrix2 o) {
final Float64List oStorage = o._m2storage;
_m2storage[0] = _m2storage[0] + oStorage[0];
_m2storage[1] = _m2storage[1] + oStorage[1];
_m2storage[2] = _m2storage[2] + oStorage[2];
_m2storage[3] = _m2storage[3] + oStorage[3];
}