* lib/filenamecat-lgpl.c (longest_relative_suffix): Remove.
(mfile_name_concat): Always make BASE a suffix of the result, as
cp expects this. To implement this, separate with '.' instead of
'/' in some rare cases. Clarify spec to say ./BASE not BASE.
* tests/test-filenamecat.c (main): Adjust tests to match
current behavior. Check that BASE_IN_RESULT points to
a copy of BASE and is a suffix of the resultk, and that DIR
is a prefix of the result that is no longer than the prefix
indicated by BASE_IN_RESULT.