wctomb() failing unexpectedly

[Jukka A. Ukkonen]

Has anyone else noticed that wctomb() returns -1
and sets errno to EILSEQ on any and all unicode
code points larger than 0xff when LC_CTYPE is
set to any UTF-8 locale?
Another symptom of something going wrong is that
proper UTF-8 encoding for code point 0xff would be
two bytes 11000011 10111111, but wctomb() returns
it simply as one byte 11111111.
I noticed this on FreeBSD 10.3-STABLE r299892.
The same thing might happen on other platforms as
well, but I just don't know it yet.

--jau