Utility: removed Debug operator<< overload for char.

Chars are now printed as integers. It is more intuitive for the user --
when aliases such as std::int8_t are used, expected output is number,
not some weird and possibly harmful character. Printing chars as
characters can be always done by converting them to std::string:

    Debug() << std::string() + 'a';
    Debug() << std::string(1, 'a');

It might cause slight performance degradation, but there are worse
bottlenecks than this. Moreover, who cares about performance in casual
debug output anyway.