Also modified ISR handler logic to account for the flag. This fixes isrExit() deadlock in Python interactive mode and prevents a more generic problem of a spurious ISR call after mraa_gpio_isr_exit() is run. Closes #268. Signed-off-by: Alex Tereschenko <alext.mkrs@gmail.com> Signed-off-by: Brendan Le Foll <brendan.le.foll@intel.com>