color detection is wrong in NCstyle

[hramrach]

NCurses.cc

    yuiMilestone() << "have color = " << ::has_colors()  << std::endl;

    if ( want_colors() && ::has_colors() )
    {
        if ( ::start_color() != OK )
            throw NCursesError( "start_color() failed" );

        NCattribute::init_colors();
    }

NCattribute.h

inline static int colors()      { return _colors ? _colors : ::COLORS; }

NCattribute.cc

    yuiMilestone() << "Init " << term_t << " using " << ( NCattribute::colors() ? "color" : "bw" )

                   << " => " << MaxStyleSet << " styles in " << styleName << std::endl;

NCattribute::colors() is used to detect colorness but it returns non-false regradless of NCattribute::init_colors() being called or not.

[hramrach]

so maybe add a flag that is set when NCattribute::init_colors() is called?