This addresses comments in #1956 and #1079. In particular, this is useful
when both endstops are stationary on a CoreXY system, and the Y axis needs
to be homed before the X so the flags are aligned.

Introduced in commit 697ee2dc and later spread to other files.

I.e., when acceleration * steps per mm > 2,000,000.
This was done by changing MultiU24X24toH16 to take a 32b bit operand.
Removed the claim that stepper.cpp uses the Leib algorithm.

example_configurations\K8200\Configuration.h:
* merge upstream changes from default Configuration.h manually
* add some machine specific comments

- Potentially addressing #1911

- Change some `previous_` time vars to `next_` so an add only happens
at intervals
- Fix `HEATER_0_USES_MAX6675` polling too frequently, or not at all

lcdDrawUpdate = 2 helped a lot!

- Prevent `Z_SAFE_HOMING` from homing Z twice in some cases
- Allow `G28` with XYZ values of 0 to explicitly set the position
- Don’t add `home_offset` when setting XYZ explicitly in `G28`
- Add `code_has_value` function to check for the presence of a numeric
value (could just test for space or nul to allow other types of values)

- MENU_ITEM causes lcd_quick_feedback to be called, so only those calls
to `lcd_goto_menu` outside of the `MENU_ITEM` macro need to set the
`feedback` flag when calling `lcd_goto_menu`.

- Replace “Mendel” with “RepRap”

- It’s inline here, but could be a macro and duplicated for
`planner.cpp`

- Use `line_to_current` in place of `plan_buffer_line`

where the hardware is available.
Fix for #1873