Keep "astyled" reformatting

With the introduction of the #if ENABLED(…)

reads better than

* Fix a couple of renames omission and macro expansion errors.

- For some reason it’s easy to forget what BT stands for, but it
doesn’t need an abbreviation.

The compiler may be able to optimize if it knows an array won’t be
changing.

Note that newer versions of the IDE can still
be made to support compilation for the older boards.

replace extruder_multiply with extruder_multiplier
like feedrate_multiplier or volumetric_multiplier

Makes the output on the LCD adjustable.

- For better encapsulation add inlines for each prepare_move type
- Move controllerFan vars inside the function as statics
- Some formatting cleanup
- Rename `ClearToSend` as `ok_to_send`

this PR replaces some bools with one char. this will safe 3 bytes and should also be sometimes a little bit faster.

- Add `M111` as a standard option to set the debug level
- Implement `DEBUG_ECHO` in `process_commands`
- Other debug levels (e.g., `DEBUG_DRYRUN`) need more work

- Include the current Z when raising the axis after and between probing
- Add `sync_plan_position_delta` for parity with `sync_plan_position`
- Clean up and clarify `M48`, `dock_sled`, and others

This rolls back to commit 06f767d608.

Fix for #1460.

Seems to work with only one extruder. Can't test this myself with more.

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.

- Address #1262 by leaving values as set
- Rename `add_homing` to `home_offset`

- 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

Warning: suggest parentheses around comparison in operand of &

pretty much helped.