The issue seems to be that object(Thread.Thread) for instance should fall back to 7.8 behavior, which should become object. Its simply handled differently in the 7.9 precompile.
Yes, I thought it was something like that. The reason for the failure is that the 7.8 precompiler behaviour was considered broken.
I have a fix, that enables the old behavior when !api (when its not specified on the command line).
I think that I'd prefer a backport of the api=3 fixes from 7.9, since it's a silent broken success.