Added permissive flag to Makefile

[ahbrosha]

Fixed compile error mentioned in #31

[tillepille]

According to this it's probably not really a good fix.

I have very little experience with gcc and c++ in general, but I think it would be good to investigate more into the RCSwitch library, if its possible to update or fix the bug there, if it's still there..

[ahbrosha]

This is clearly more a hotfix, than a good solution. However, it keeps the code compilable. I would like to further investigate the RCSwitch code in the near future, maybe during the weekend.

[thoro2105]

Sorry for my bad english.

233/5000
Despite the addition of the file "Makefile" as described, there is a compiling error in the latest version of Raspbian.
The addition in the line is unfortunately not enough. It still comes to the error:

Assembler message:
Fatal error: can't creante RCSwitch.o: no authorization
make: *** error 1

Which inputs can you force a compilation here?