Dimmer.h issues with ATmega 128
The Dimmer library doesn't support Atmega128/164/16/32. It has

#if defined(__AVR_ATmega1280__) || defined(__AVR_ATmega2560__)
#define DIMMER_TIMER 4
#elif defined(__AVR_ATmega32U4__)
#define DIMMER_TIMER 3
#else
#define DIMMER_TIMER 2
#endif


For the Atmega128/164/16/32 it will use timer 2. The main errors are:

'OCR2A' was not declared in this scope
'TCCR2A' was not declared in this scope
'TCCR2B' was not declared in this scope
'TIMSK2' was not declared in this scope


Possible solution:

You could try to use timer 3. Only you need to change the timer number in Dimmer.h and in Dimmer.cpp on line 159 change TIMSKx(DIMMER_TIMER) = 0x02 perhaps to bitSet(ETIMSK, 3);. Check the datasheet. I can't test it, I don't have the chip.