scopes: improve C preprocessor macro robustness

scopes: improve C preprocessor macro robustness

For pin and LED control related #define directives use C language
compound statements. This lets call sites use the macros in intended
ways (like regular function calls) without needing to worry about their
implementation details, or suffering from unexpected behaviour.

Strictly speaking the single statement variants don't require the
wrapper, but I've added one for improved future maintenance.