libstdc++: Restore printing of assertion messages [PR102100]

libstdc++: Restore printing of assertion messages [PR102100]

My changes for PR 101429 broke the _-replacement_assert function,
because we now always just abort without printing anything. That's
because I added checks for _GLIBCXX_HOSTED and _GLIBCXX_VERBOSE, but the
checks are done before those get defined.

This adds a new macro which is set
by the sed command in include/Makefile, once the HOSTED and VERBOSE
macros have been set by the configure script.

libstdc++-v3/ChangeLog:

	PR libstdc++/102100
	* include/Makefile.am (c++config.h): Define
	_GLIBCXX_VERBOSE_ASSERT based on configure output.
	* include/Makefile.in: Regenerate.
	* include/bits/c++config: Fix condition for verbose assertions.