I think -Wshadow is a good feature to avoid silly mistakes, like:

voidf() {boolflag= false;// some codeif(condition) {boolflag= true;    }// some more codeif(flag) {// want to do something, but flag is never true    }}

I have wasted some time on my silliness recently. So I think it's good to have this warning turned on, and when I do it, SPI and EEPROM libraries make the compiler complain.

This PR just renames those parametes, nearly no cost.