[Dillo-dev] Avoid ctype(3) abuses

Hello! Most ctype(3) functions usage abuses an undefined behavior of passing values outside integers outside EOF or the range representable as unsigned char. On NetBSD 11 and newer such incorrect behaviors crashes applications violating that and due that Dillo easily crash by just visiting, e.g. <https://www.NetBSD.org/>. For possible further information please give a look to <https://man.NetBSD.org/ctype.3#CAVEATS>. I have grep-ed all such uses and added the relevant cast to uchar_t similar to other ctype(3) calls already present and in that way I can also confirm that Dillo no longer crashes. Attached in this email you can find a patch to address that. Thank you!