reading wide characters manually. With this change, they now use
fgetwc(). To make this work, we use an internal version of fgetwc()
with a few extensions: it takes an mbstate * because non-wide streams
don't have a built-in mbstate, and it indicates the number of bytes
read.
vfscanf() now resembles vfwscanf() more closely. Minor functional
improvements include working xlocale support in vfscanf(), setting the
stream error indicator on encoding errors, and proper handling of
shift-based encodings. (Actually, making shift-based encodings work
with non-wide streams is hopeless, but the implementation now matches
the broken specification.)
d7af8cf14b