GC write barrier stuff; faster version of .add(); fixed inheritance access controls
use permanent references to fields. it's not like the offset is going to change, and the list can't be changed after the constructor, so we're doing pointer math for nothing otherwise.
pinned writing, for loading data faster-than-using-add-but-not-as-fast-as-load when you don't know up-front exactly how much you'll be loading
speed up MonoObject* add() method, with correct wbarrier behaviour
ditch loading 'add' from reflection; fixed a type issue in MonoObject* add method