DcsBios.h

extern unsigned int leds; //put this line before namespace (beginning of code)

[...]

class LEDSR : ExportStreamListener {
    private:
        void onDcsBiosWrite(unsigned int address, unsigned int value);
        unsigned char pin_;
        unsigned int address_;
        unsigned int mask_;
        unsigned int leds_;
    public:
        LEDSR(unsigned int address, unsigned int mask, char pin);
};