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.

- Potentially addressing #1911

Updated documentation in Configuration.h.
Cleaned up and commented some code relating to Z_PROBE_ENDSTOP.
Separated Z_MIN_ENDSTOP and Z_PROBE_ENDSTOP completely.

Documented some additional areas that should be addressed if Z_PROBE is
fully separated from Z_MIN or Z_MAX.
Fixed a documentation error in sanity checks. Servos start at 0 not 1.

This rolls back to commit 06f767d608.

- Fix `prepare_move` function not calling `adjust_delta`
- Add more shorthand for plan_buffer_line.
- Fix wrong `federate` usage, assuming they are all mm/m
- Minor `stepper.cpp` cleanup

Code cleanup for Z_PROBE_AND_ENDSTOP.
Added Z_PROBE_PIN to pins_RAMPS_13.h

- Add some documentation to planner and stepper headers
- Patch up RAMBO pins with undefs
- Add `sync_plan_position` inline to set current XYZE
- Swap indices in `extruder_offset` to fix initialization values

Typo fixes in comments in existing code.

- Patched up for most included configurations

- Fix a bug reading `code_value` for `M503 Sn`
- Hide and remove unused variables

Z_DUAL_ENDSTOPS is a feature to enable the use of 2 endstops for both Z
steppers - Let's call them Z stepper and Z2 stepper.
That way the machine is capable to align the bed during home, since both
Z steppers are homed.
There is also an implementation of M666 (software endstops adjustment)
to this feature.
After Z homing, this adjustment is applied to just one of the steppers
in order to align the bed.
One just need to home the Z axis and measure the distance difference
between both Z axis and apply the math: Z adjust = Z - Z2.
If the Z stepper axis is closer to the bed, the measure Z > Z2 (yes, it
is.. think about it) and the Z adjust would be positive.
Play a little bit with small adjustments (0.5mm) and check the
behaviour.
The M119 (endstops report) will start reporting the Z2 Endstop as well.

- Patch up macros in stepper.cpp

- Use named axis indexes, `X_AXIS` etc.
- Replace `block.steps_A` with block.steps[A]`
- Replace `A_segment_time` with `segment_time[A]`
- Add `A_AXIS`, `B_AXIS` for `COREXY` axes
- Conditional compile based on `EXTRUDERS`
- Add BLOCK_MOD macro for planner block indexes
- Apply coding standards to `planner.h` and `planner.cpp`
- Small optimizations of planner code
- Update `stepper.cpp` for new `block` struct
- Replace `memcpy` with loops, let the compiler unroll them
- Make `movesplanned` into an inline function

- Addressing #1625

- Add `Conditionals.h` with calculated configuration values
- Add `SanityCheck.h` with checks for configuration errors
- Remove equivalent code from all configurations
- Move error checks from some sources to `SanityCheck.h` also
- Fix initialization of count_direction in stepper.cpp

When one hit "Stop Print" option in LCD menu, the command buffer was not
cleared. The printer keep moving until the buffer has been emptied.
Actually I could not clear the command buffer as well.. I don't know
why, it doesnt work as expected.
I need to implement a routine inside Stepper ISR to handle such
situation.

The Check Endstop logic must be:

if (current_block->steps_x != current_block->steps_y || (TEST(out_bits,
X_AXIS) == TEST(out_bits, Y_AXIS)))
if (TEST(out_bits, X_HEAD))

not

if (TEST(out_bits, X_HEAD) && (current_block->steps_x !=
current_block->steps_y || (TEST(out_bits, X_AXIS) == TEST(out_bits,
Y_AXIS))))

Same applies for Y axis.

- Add BIT and TEST macros
- Add _APPLY_ macros to stepper.cpp to help with consolidation
- Consolidate code in stepper.cpp using macros
- Apply standards in stepper.cpp
- Use >= 0 instead of > -1 as a better semantic
- Replace DUAL_Y_CARRIAGE with Y_DUAL_STEPPER_DRIVERS

- Moved sanity-checks to Marlin_main.cpp
- Applied to other configuration files
- Fixed formatting of ABL output
- Passing verbose level to probe_pt
- Miscellaneous cleanup
- Put CONFIG_STEPPERS_TOSHIBA into Configuration.h

The X_Axis could not home to min while Y_Max endstop was trigged.

- Both TMC, L6470 and pin-driven drivers work.
- All can be mixed and matched as needed.

Fixed how stepper ISR figure it out when the head (extruder) is going to
Min or Max direction.
Added Homing to Max Endstops.

removed function step_wait() from stepper.cpp because its used nowhere.