Fix #10505

Also simplify logic on all ARM-based interrupts. Now, it is REQUIRED to properly configure interrupt priority. USART should have highest priority, followed by Stepper, and then all others.

This is an initial cut for feedback, updated for 2.0.x.

Chamber temperature is currently reported along with hot end and bed
temperatures to serial. The format is just like that used for hot end
and bed temperatures, but using 'C' prefix. As there is no heater,
target is always 0. Is this appropriate, is there a better way to report
chamber temperatures?

Chamber temperatures are not reported on the LCD in any way.

When auto chamber fan is enabled, it currently just uses the same
temperature threshold as the other auto controlled fans.

As the chamber temperature is not connected to any heater, it doesn't
undergo mintemp/maxtemp monitoring. This would need to change in the
future if chamber heating became a feature.

- Watchdog reset during SD Card initialization.
- Move `DebugMonitor` to `DebugMonitor_Due.cpp`.
- Since the watchdog is enabled on boot do extra resets during init.
- Have `thermalManager` do watchdog reset before its ISR starts to prevent reset.
- Ensure that timers are stopped before reprogramming them to address tone issues.
- Improve SAM3XE reset when reflashed through the native port.

- Fix Autotune Thermal Protection
- Make 2 constants in autotune configurable

Fix #9906

Fixes issue found in #8779

Fix #8710

Travis is having problems at:  https://github.com/MarlinFirmware/Marlin/pull/8560   

So...   doing a direct commit to get things correct.   Bugfix_v1.1.x does not have this bug.  Nothing needs to be done to that branch.

Add and bugfix pins

include LPC1768 syntax for M42

couple more pin_t changes

consistency

change M42 to R, P format

Revert "change M42 to R, P format"

This reverts commit 01f12f579e.

Fixes for 2 "... not declared in this scope" compiler errors.

Replace ARDUINO_ARCH_AVR with __AVR__ to better detect architecture for non-Arduino dev environments.  Resolves compile failure in PIO for 8-bit Teensduino targets

More info:
https://forum.pjrc.com/threads/33234-Using-Teensyduino-Selecting-Teensy-3-2-3-1-board-has-incorrect-platform-define
http://www.atmel.com/webdoc/avrlibcreferencemanual/using_tools_1using_avr_gcc_mach_opt.html