libstdc++: Allow std::condition_variable waits to be cancelled [PR103382]

libstdc++: Allow std::condition_variable waits to be cancelled [PR103382]

std::condition_variable::wait(unique_lock<mutex>&) is incorrectly marked
noexcept, which means that the __forced_unwind exception used by NPTL
cancellation will terminate the process. It should allow exceptions to
pass through, so that a thread can be cleanly cancelled when waiting on
a condition variable.

The new behaviour is exported as a new version of the symbol, to avoid
an ABI break for existing code linked to the non-throwing definition of
the function. Code linked against older releases will have a reference
to the @GLIBCXX_3.4.11 version, andcode compiled against the new
libstdc++ will get a reference to the @@GLIBCXX_3.4.30 version.

libstdc++-v3/ChangeLog:

	PR libstdc++/103382
	* config/abi/pre/gnu.ver (GLIBCXX_3.4.11): Do not export old
	symbol if .symver renaming is supported.
	(GLIBCXX_3.4.30): Export new symbol if .symver renaming is
	supported.
	* doc/xml/manual/evolution.xml: Document change.
	* doc/html/manual/api.html: Regenerate.
	* include/bits/std_mutex.h (__condvar::wait, __condvar::wait_until):
	Remove noexcept.
	* include/std/condition_variable (condition_variable::wait):
	Likewise.
	* src/c++11/condition_variable.cc (condition_variable::wait):
	Likewise.
	* src/c++11/compatibility-condvar.cc (__nothrow_wait_cv::wait):
	Define nothrow wrapper around std::condition_variable::wait and
	export the old symbol as an alias to it.
	* testsuite/30_threads/condition_variable/members/103382.cc: New test.