This patch revises the I2C and GPIO initialization code to always be
run during platform boot rather than within each process that requires
it.
This patch also revises the gpio-output example to use a pin that is
set as an output by the default pinmux configuration. Previously, it
used a pin that was set as an output by the pinmux configuration that
is in effect when the OS does not change the pinmux configuration.
This patch introduces an example application to demonstrate how to use
GPIO driver APIs to manipulate interrupt pins.
The application uses default galileo pinmux initialization and sets
the GPIO 5 (IO2) as output pin and GPIO 6 (IO3) as interrupt. It toggles
the output pin stat at every half second in order to emulate an interrupt.
This triggers an interrupt and the application callback is called.
