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

Re-ARM has been tested.  AVR has not been tested.

1) moved all cpu specific items to files in the low level HAL directory
for that CPU (pinDebug_Re-ARM.h & pinsDebug_AVR_8_bit.h

2) added pinsDebug.h to the top level directory

3) modified HAL_pinsDebug.h to select the correct support file for the
selected CPU

4) Patched sanitycheck to stop throwing false errors.  A long term
solution will be done

5) misc changes & bug fixes
arduino.cpp - included macros.h to fix a missing definition
pinmap_re-arm.h - removed a duplicated line.
pinmapping.h - changed from "ENABLED" to "defined" to fix a compile
error

======================================================================

split SanityCheck up, improve pinsDebug system

======================================================================

switch to latest pins_RAMPS_RE_ARM.h

Implement AVR Platform

Includes:
  *firmware version / branch / date.
  *extruder count
  *board information (name, serial details, power supply type)
  *thermistors (names, min/max temperatures)
  *printer statistics (PRINTCOUNTER details)

Thanks to @thinkyhead for contributions.

Following up on #3231

Hopefully this is helpful to organization and future expansion….

Hopefully this is helpful to organization and future expansion….

Hopefully this is helpful to organization and future expansion….