GitLab

Detail:
* Fixes register corruption in GPIOPullDirection.
* Pre-seeds the soft copies with the values from the datasheet (so no need for a function
  to read them). This should also help other models of Pi which assumed they were all
  disabled when it seems they are not!
* Reworks the SDIO driver to call through to the GPIO so that its softcopy is kept in
  sync, and so the settings do something on a Pi 4 at all.
Admin:
  Tested on Pi4 and a Pi 3B+.

Version 0.91. Tagged as 'HAL_BCM2835-0_91'