libstdc++: Fix std::any pretty printer [PR 68735]

libstdc++: Fix std::any pretty printer [PR 68735]

This fixes errors seen on powerpc64 (big endian only) due to the
printers for std::any and std::experimental::any being unable to find
the manager function.

libstdc++-v3/ChangeLog:

	PR libstdc++/65480
	PR libstdc++/68735
	* python/libstdcxx/v6/printers.py (function_pointer_to_name):
	New helper function to get the name of a function from its
	address.
	(StdExpAnyPrinter.__init__): Use it.