ops.cc (stat_type): Define alias for struct stat and use throughout the file.

ops.cc (stat_type): Define alias for struct stat and use throughout the file.

	* src/filesystem/ops.cc (stat_type): Define alias for struct stat and
	use throughout the file.
	(make_file_type): New function.
	(file_size(const path&, error_code&)): Report an error for anything
	that isn't a regular file.
	(status(const path&), symlink_status(const path&)): Do not throw for
	file_type::not_found.
	(temp_directory_path()): Check additional environment variables.
	* testsuite/experimental/filesystem/operations/exists.cc: New.
	* testsuite/experimental/filesystem/operations/file_size.cc: New.
	* testsuite/experimental/filesystem/operations/status.cc: New.
	* testsuite/experimental/filesystem/operations/temp_directory_path.cc:
	New.

From-SVN: r223224