improve <boost/config.hpp>

From: Gero Peterhoff (g.peterhoff_at_[hidden])
Date: 2023-02-19 22:27:20

Hi,
for more compatibility with existing boost-macros/defines I came up with - see attachment.
1) Is that correct in principle?
2) Problem: for BOOST_NO_CXX23_HDR_XXX I use __has_include. However, __has_include is not guaranteed to exist. How about the solution?
3) Did I miss useful things?

thx
Gero