fs_path.h (path::_List): Use vector instead of list.

fs_path.h (path::_List): Use vector instead of list.

	* include/experimental/fs_path.h (path::_List): Use vector instead of
	list.
	* python/libstdcxx/v6/printers.py (StdExpPathPrinter): Adapt.
	* src/filesystem/path.cc: Use std::prev instead of decrementing
	rvalues. Fix whitespace.
	* testsuite/experimental/filesystem/path/decompose/parent_path.cc:
	Do not decrement iterators before begin.

From-SVN: r222702