PR libstdc++/90220 Fix std::any_cast for function pointers

PR libstdc++/90220 Fix std::any_cast for function pointers

	PR libstdc++/90220 (partial)
	* include/std/any (any_cast<T>(any*), any_cast<T>(const any*)): Do
	not attempt ill-formed static_cast to pointers to non-object types.
	* testsuite/20_util/any/misc/any_cast.cc: Test std::any_cast with
	function types.

From-SVN: r270538