Allow `ENABLED`, `DISABLED`, `PIN_EXISTS`, and `BUTTON_EXISTS` to take multiple arguments. Also add:
- Alias `ANY(...)` for `!DISABLED(...)`
- Alias `ANY_PIN(...)` for `PIN_EXISTS(a) || PIN_EXISTS(b) ...`
- Alias `EITHER(A,B)` for `ANY(...)`
- Alias `ALL(...)` and `BOTH(A,B)` for `ENABLED(...)`
- `NONE(...)` for `DISABLED(...)`

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

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

- Remove `print_job_timer.stop()` from `disable_all_heaters`
- Call `print_job_timer.stop()` for relevant `disable_all_heaters()`.
- Split up `kill()` for watchdog interrupt safety

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.