Bug fixes for timers, added some wdt support for limit debounce.

- Typo in timer def,
- Handle 8 bit timers correctly,
- Don't skip TOP count in CTC mode
- added SREG for atomic bit operations

sim/avr/wdt.h

@@ -1 +1,11 @@
+#define WDTCSR wdt
+#define WDP0 0
+#define WDP1 1
+#define WDP2 2
+#define WDE  3
+#define WDCE 4
+#define WDP3 5
+#define WDIE 6
+#define WDIF 7
+
 uint16_t wdt;