Given the following example, using (rnrs unicode): (string-foldcase "ΜΈΛΟΣ")
The expected result is "μέλοσ"; see R6RS libraries section 1.2. However instead Guile's result is "μέλος". Note that although Σ usually downcases to σ, at the end of a string it's ς. This test shows a limitation of defining string-foldcase as simply (string-downcase (string-upcase str)).
