[2.0.x] Fix Ender 4 compilation, add more AVRs to Makefile

- Assign 243 (like EFB) as Ender-4/CR-8 board ID
- Add to `Makefile`
- Add to `pins.h`

Addressing #10200

Fix #10256

Do the Z lift normally before setting Z back to its prior value. But do the Z lower using spoofing. This should produce proper symmetrical movement.

This ensures that steppers that share an enable pin will only be disabled for a miniscule time.

See https://github.com/MarlinFirmware/Marlin/issues/10246#issuecomment-377146936

Pending a more complete solution to tool-change Z deviation.

Followup to #10250

[2.0.x] Improvements to general and delta homing

Followup to 436e5b7e

Some languages will need to be updated for proper phrasing

Followup to 3007eee2

Fixes #10137

See https://github.com/MarlinFirmware/Marlin/commit/941e9bd329c4831909b4d010f78a4a1d900e5b00#commitcomment-28262166

Fixes #10209

Fix #10232

From #10204 by @adriancuzman

- And implement the `backtrace()` function call

The `_O2` attribute is no longer needed on the malyanlcd function, and the macros have broken timer numbers - reset this to a function to return the right device. Also fix the bit order cast in SPI.