Create timer0 overflow interrupt service routine for all ATtinies not just 24, 44 and 84

Author: Torben Nielsen

Diff for: cores/arduino/wiring.c

@@ -39,7 +39,7 @@ volatile unsigned long timer0_overflow_count = 0;
 volatile unsigned long timer0_millis = 0;
 static unsigned char timer0_fract = 0;
 
-#if defined(__AVR_ATtiny24__) || defined(__AVR_ATtiny44__) || defined(__AVR_ATtiny84__)
+#if defined(TIM0_OVF_vect)
 ISR(TIM0_OVF_vect)
 #else
 ISR(TIMER0_OVF_vect)