Enable reception for ATtinyX4 and ATtinyX5

[cyosp]

Hi Suat,

This pull request allows to enable reception for ATtinyX4 and ATtinyX5 using PinChangeInterrupt library of NicoHood.
I've tested with success on ATtiny85.

Best regards,
CYOSP

[fingolfin]

The above changes, and similar changes below, are not acceptable. These #ifdefs are there for an good reason: To keep code size low for people who do not need to receive data.

[vlad2005]

@cyosp
I try to use these modifications to be able to use RCSwitch on ordinary digital pin. My board is an arduino pro mini and use suggestion from @fingolfin to include necessary lib and code. But it's seem that not working.
Where can i have an discussion about that?
P.S. I think that is very important to make RCSwitch to work on regular pin because sometime external interrupts need for other tasks. In my case i need to precisely count revolution for two motors and using PIN CHANGE INTERRUPT is a bit slower because need to check witch pin got signal.
Thanks!

L.E. sorry, i'm a bit novice with github. I will continue discussion on RCSwitch fork make by @cyosp