* Fix up GPIO macros
* Fix up send string macros
`string` arguments must not be parenthesized
* Fix up miscellaneous macros
* Make indentation uniform (4 spaces)
* Make #ifdef vs #if defined usage consistent
* Reorder standard includes
* Revert indentation changes as per review comments
* Revert #if defined(__AVR__) → #ifdef __AVR__ change
* Change 2 space indent to 4 spaces on a couple of lines
* Replace include guard with #pragma once
c69060465e