[C++ RFH/Patch] PR 52892 (and others)

[Paolo Carlini]

.. two additional remarks (maybe obvious, I don't know):
- It also appears to work - for sure for all the tests in c++/52892 + 
the tests in c++/52282 not involving data members (eg, the original one) 
- simply unconditionally calling STRIP_NOPS right after the 
cxx_eval_constant_expression at the beginning of 
cxx_eval_call_expression (or calling it only when, after the fact, we 
know it wraps a function pointer).
- Grepping in semantics.c reveals that in quite a few other places we 
make sure to STRIP_NOPS before checking for ADDR_EXPR, it seems a 
general issue.

Thanks,
Paolo.