Chain assignments

[simonlindholm]

void foo(Thing* thing) {
    thing->a = 0;
    thing->b = 0;
}

or

void foo(Thing* thing) {
    thing->a = 0;
    thing->b = thing->a;
}

->

void foo(Thing* thing) {
    thing->b = thing->a = 0;
}

Could use the same pass as #99, maybe.