* python/libstdcxx/v6/printers.py (SingleObjContainerPrinter): Allow
display_hint to be set by subclasses.
(StdVariantPrinter): Use array for display_hint. Adjust output to be
more similar to std::any and std::optional output.
(register_type_printers): Add type printers for basic_string_view
typedefs and experimental::any. Adjust type printers for
fundamentals_v1 templates to match fundamentals_v2 and later.
* testsuite/libstdc++-prettyprinters/cxx17.cc: New.
From-SVN: r240234
