Don't know what the standard says about it, but the feature seems reasonable
and other compilers handle it this way.
git-svn-id: svn://svn.cc65.org/cc65/trunk@42 b7a2c559-68d2-44c3-8de9-860c34a00d81
Change the isxxx functions to correctly handle values outside of character
range.
git-svn-id: svn://svn.cc65.org/cc65/trunk@33 b7a2c559-68d2-44c3-8de9-860c34a00d81