This is another attempt to reduce how often the assertions are
evaluated, so that code which doesn't try to use the function objects
doesn't need them to be invocable.

For _Rb_tree we access the _M_key_compare object directly, so can't put
the assertions in an accessor function for it. However, every invocation
of _M_key_compare is accompanied by a use of _S_key, so the assertions
can be put in there.  For _Hashtable there are member functions that are
consistently used to obtain a hash code or test for equality, so the
assertions can go in those members.

	PR libstdc++/85965
	* include/bits/hashtable.h (_Hashtable::~_Hashtable()): Remove static
	assertions from the destructor.
	* include/bits/hashtable_policy.h (_Hash_code_base::_M_hash_code):
	Move static_assert for hash function to here.
	(_Hash_table_base::_M_equals): Move static_assert for equality
	predicate to here.
	* include/bits/stl_tree.h (_Rb_tree::_S_value(_Const_Link_type)):
	Remove.
	(_Rb_tree::_S_key(_Const_Link_type)): Move assertions here. Access
	the value directly instead of calling _S_value.
	(_Rb_tree::_S_value(_Const_Base_ptr)): Remove.
	(_Rb_tree::_S_key(_Const_Base_ptr)): Do downcast and forward to
	_S_key(_Const_Link_type).
	* testsuite/23_containers/set/85965.cc: Check construction,
	destruction, assignment and size() do not trigger the assertions.
	* testsuite/23_containers/unordered_set/85965.cc: Likewise.
	* testsuite/23_containers/map/48101_neg.cc: Call find and adjust
	expected errors.
	* testsuite/23_containers/multimap/48101_neg.cc: Likewise.
	* testsuite/23_containers/multiset/48101_neg.cc: Likewise.
	* testsuite/23_containers/set/48101_neg.cc: Likewise.
	* testsuite/23_containers/unordered_map/48101_neg.cc: Likewise.
	* testsuite/23_containers/unordered_multimap/48101_neg.cc: Likewise.
	* testsuite/23_containers/unordered_multiset/48101_neg.cc: Likewise.
	* testsuite/23_containers/unordered_set/48101_neg.cc: Likewise.

From-SVN: r271323