Merge pull request #4 from niesteszeck/master

repaired portSAVE_CONTEXT() for atmega2560
Pins 5 and 6 on the Arduino UNO and pins 7 and 13 in the Arduino MEGA
TIMER0 use to control the PWM, Timer 0 as being used by DuinOS, insert
the option to disable by setting the property using your
DISABLED_BY_DUINOS