PROPOSED PATCH: Robustify cp_fold_obj_type_ref() for ObjC++ use

[Zack Weinberg]

Steven Bosscher <s.bosscher@student.tudelft.nl> writes:

> while others are somehow allowed to completely rewrite the C++
> lexical analysis in stage3 and not get a single question about that
> from any C++ maintainer.

For the record: that was the 'compile-time performance improvement'
that I got dispensation to submit by September 19.  I see that I
neglected to mention this in my commit message, and missed the
deadline by one day.  Sorry about that.

Patches I do to the C++ front end tend to be extensively discussed
with Mark off-list.  This is purely a matter of convenience - I will
make efforts to conduct more public discussions in the future.

zw