* module/ice-9/ftw.scm (scandir)[leaf]: Only add NAME when RESULT is a
pair.
[down]: Ignore RESULT.
Start with #f instead of the empty list.
* test-suite/tests/ftw.test ("scandir")["flat file"]: New test.
* doc/ref/misc-modules.texi (File Tree Walk): Update `scandir'
documentation accordingly.