PR libstdc++/59170
	* python/libstdcxx/v6/printers.py (StdListIteratorPrinter.to_string)
	(StdSlistIteratorPrinter.to_string, StdVectorIteratorPrinter.to_string)
	(StdRbtreeIteratorPrinter.to_string)
	(StdDequeIteratorPrinter.to_string): Add check for value-initialized
	iterators.
	* testsuite/libstdc++-prettyprinters/simple.cc: Test them.
	* testsuite/libstdc++-prettyprinters/simple11.cc: Likewise.

From-SVN: r243692