The idiomatic way of coping with signed char vs unsigned char (which

The idiomatic way of coping with signed char vs unsigned char (which
did not come from stdio read functions) in the presence of ctype
macros, is to always cast to (unsigned char).  casting to (int) for
a "macro" which is documented to take int, is weird.  And sadly wrong,
because of the sing extension risk..
same diff from florian