ecere/com; compiler/libec: (#1087) Fixed class:struct issues

ecere/com; compiler/libec: (#1087) Fixed class:struct issues
- Watches on a derived class:struct member whose base class has end-padding did not work (e.g. AddCharAction)
- Alignment issues as derived classes are bundled together in a single struct
- Derived class offset was not correct
- OnGetString, OnGetDataFromString and JSON did not add class offset but should have
- typed_object& methods when called as a member of a class:struct did not have proper reference level (the address of the class:struct instance should be passed)