= integrated JohnRB's PCINT0 ISR that uses a fixed pin mapping to lower ISR overhead.
- requires RX3S_V2 pin mapping and non DUAL_AIL config, so that
- AIL_IN_PIN = PORTB0 (pin 8)
- ELE_IN_PIN = PORTB1 (pin 9)
- RUD_IN_PIN = PORTB2 (pin 10)
- AUX_IN_PIN = PORTB3 (pin 11)
= adding LED_TIMING_START and LED_TIMING_STOP macros,
- instead of having to set and clear PB5 bit each time.
- uncomment #define LED_TIMING to disable LED messages and enable the new macros.
= fixes to mod_pcint0 isr.
- parenthesize (1 << n) operation.
- ensure rx_portb_sync is set only if the pulse if valid.
= updated mod_pcint0 isr from johnrb
= reduced cut-and-paste code in the ISR by turning the common code into a parametrized CHECK_CHANNEL macro.
= move the #define MOD_PCINT0 part to inside #define RX3S_V2 since it is only valid for that device.
= added original comments.
= fixed macro multiline definition. was not compiling right in the first place.
Merge branch 'mod_pcint0'
= fixed MM and DD ordering when using the system date.

= used all caps for TODAY var.