Program Space Utilities (pgmspace.h)

Other support packages are referencing `pgmspace.h`. E.g. [ArduinoCore-avr](https://github.com/arduino/ArduinoCore-avr/search?p=1&q=pgmspace.h) or [arduino-esp32](https://github.com/espressif/arduino-esp32/blob/master/cores/esp32/pgmspace.h). We are experimenting with porting some prototyp to the Portenta Machine Control Board. Unfortunatelly our code does not compile anymore cause one of our dependencies depends on `pgmspace.h`.

I could not find program space utilities (usually contained in `pgmspace.h`) in this drivers so far. Are there program space utilities defined in this drivers somewhere?

Start by reviewing the pgmspace.h implementations linked from ArduinoCore-avr and arduino-esp32, then search ArduinoCore-mbed and its dependencies for existing program-space utilities. Define which compatibility surface is needed for the Portenta Machine Control Board and verify that the reported dependent code compiles against it.

Written by the indexing model from the issue text.