-normalize `env` and `board` to lowercase naming convention.
-make board `name` follow descriptive convention.
-implement `-fsingle-precision-constant` compile optimization per https://github.com/MarlinFirmware/Marlin/pull/11178#issuecomment-401673901
-fix typo in 5DPRINT entry.

Indeed the HAL does not need to be mucked around with to expose ATmega2560 pins not available as numbers on the MEGA board, I'll need to update the wiki with that tidbit and a reference to the pin-mapping comment in `fastio_1280.h`.

Co-Authored-By: bleughb <36889022+bleughb@users.noreply.github.com>

The current Marlin implementation relies on a timer interrupt to start the ADC conversion and read it. However in some circumstances the interrupt can be delayed resulting in insufficient time being available for the ADC conversion. This results in a bad reading and false temperature fluctuations. These changes make sure that the conversion is complete (by checking the ADC hardware via the HAL) before reading a value.

See: https://github.com/MarlinFirmware/Marlin/issues/11323

Co-Authored-By: vitekn <vitekn@users.noreply.github.com>

[2.0.x] Tweak some SoftPWM code

Typo fix

[2.0.x] Configure stepper drivers per axis

Co-Authored-By: teemuatlut <teemu.mantykallio@live.fi>

[2.0.x] Manual Z Start Height

* Add Multi Unit Support for Max7219 to bugfix_2.0.0

* Apply multi-MAX7219 to example configs

* Tweak some spacing, macros

Fix #11279, #11252

[2.0.x] Add support for power loss detect pin

See https://github.com/MarlinFirmware/Marlin/issues/10949#issuecomment-398540498

[2.0.x] Malyan LCD Feedrate + Better Temp Handling

When `INCH_MODE_SUPPORT` is enabled no default unit is set. This fixes it.

It takes too long to display the mesh data for large mesh's at startup.   We should consider ways to speed this up.
Perhaps it makes sense to display an entire row of the mesh instead of just one mesh point?

This reverts commit a26fdf6b68.

On a leap of faith...  I'm merging...

[2.0.x] LPC1768: Expand hardware SPI class

Prevent crash, on filament change, when printer is not homed