Updated PX4IO autostart script.

Enables the PX4IO ADC (from px4io-adc-integration branch)

Fixed connection loss / failsafe detection, added decoding of two switches

#111 px4io integrated mixing

Fix a botched merge for #106 at the same time.

Initial implementation of application access to the PX4IO relays.

The most critical one is the GPS serial port receive buffer size,
which needs to be at least 128 to support the UBLOX protocol, but it
seems a good idea for people running a FMU without a IO board to
increase the UART buffer sizes generally

this was using the wrong channel

this allows apps to set the PWM update rate. APM needs this to honor
the user configurable PWM rate setting for copters.

the device ioctl returns -ENOTTY when it hasn't handled the command

Add FIONWRITE to allow applications to sniff the amount of writable space on a descriptor. Implement this for serial devices only.

Add FIONWRITE to allow applications to sniff the amount of writable space on a descriptor. Implement this for serial devices only.

this is used by the APM build