fix handling of files of unsupported type in the walk code
if a file was of unsupported type, it was considered as 'seen' while
walking. this way it was possible to have file in the dirstate not
yielded by the walk function.
adding foo
adding bar
adding baz/bletch
test-archive-TIP/bar
test-archive-TIP/baz/bletch
test-archive-TIP/foo
test-archive-TIP/bar
test-archive-TIP/baz/bletch
test-archive-TIP/foo
Archive: archive.zip
testing: test-archive-TIP/bar OK
testing: test-archive-TIP/baz/bletch OK
testing: test-archive-TIP/foo OK
No errors detected in compressed data of archive.zip.
killed!