See https://github.com/pinchies/Marlin/pull/1#issuecomment-471388743

In reference to #11000

* Apply #pragma once in headers
* Adjust some thermistors formatting
* Misc cleanup and formatting

STM32 can reuse JTAG and SWD pins separately. Add `DISABLE_DEBUG` option to disable both interfaces and retain `DISABLE_JTAG` to disable JTAG only.

Some STM32-based boards may use multiplexed JTAG pins as IO. Up to now the `DISABLE_JTAG` option (defined in pins files) was only supported for AT90-based boards. This commit generalizes the code and adds support for boards based on STM32F1 and STM32F4.

- Clean up the API to use a `static` class instance to adhere to Marlin convention
- Add `const` position data access for read/write
- Add Storage capacity to the interface

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

Always honor minimum period on stepper pulse generation, and fix timing calculations

Signed-off-by: etagle <ejtagle@hotmail.com>