PR libstdc++/82777
	* src/filesystem/std-path.cc (path::lexically_normal): Remove dot-dot
	elements correctly.
	* testsuite/27_io/filesystem/path/generation/normal.cc: Add testcase.
	* testsuite/util/testsuite_fs.h (compare_paths): Improve exception
	text.

From-SVN: r254317