PR libstdc++/79789 fix non-reserved names in headers

PR libstdc++/79789 fix non-reserved names in headers

	PR libstdc++/79789
	* include/bits/hashtable_policy.h (__clp2): Use reserved names for
	parameters and local variables.
	* include/bits/ios_base.h (make_error_code, make_error_condition):
	Likewise.
	* include/bits/list.tcc (list::sort): Likewise.
	* include/bits/mask_array.h (mask_array): Likewise.
	* include/bits/regex.h (regex_token_iterator): Likewise.
	* include/bits/slice_array.h (slice_array): Likewise.
	* include/bits/stl_algo.h (__sample): Likewise.
	* include/std/memory (undeclare_no_pointers): Likewise.
	* include/std/type_traits (is_callable_v, is_nothrow_callable_v):
	Likewise.
	* libsupc++/exception_ptr.h (__dest_thunk): Likewise.
	* testsuite/17_intro/headers/names.cc: New test.

From-SVN: r245828