* Fixing the DUE serial port assignments: Now -1 means the SAM3x USB Device emulating a serial port, and 0 means the USB to serial adapter included as a programming port

* Improving the Fast IO port access implementation on Arduino DUE

* Implemented EEPROM emulation on Due by storing data on the internal FLASH (with wear leveling)

* Implemented a Software SPI for the ST7920 graphics display for the Arduino RAMPS for DUE, as the default one in u8glib is clocking data too fast on ARM, and the display does not understand it.

* Fixing the case where the serial port selected is the USB device

* Adding configuration for the Makerparts 3D printer (www.makerparts.net)

* Tuned MakerParts acceleration on X and Y axis so it never loses steps. Also adjusted pulses per mm to match default hw configuration

* Fine tuned Maximum acceleration for MakerParts printer

* Style cleanup

* Style cleanup (2)

* Style fixes (3)

* Fixing the DUE serial port assignments: Now -1 means the SAM3x USB Device emulating a serial port, and 0 means the USB to serial adapter included as a programming port

* Improving the Fast IO port access implementation on Arduino DUE

* Implemented EEPROM emulation on Due by storing data on the internal FLASH (with wear leveling)

* Implemented a Software SPI for the ST7920 graphics display for the Arduino RAMPS for DUE, as the default one in u8glib is clocking data too fast on ARM, and the display does not understand it.

* Fixing the case where the serial port selected is the USB device

* Adding configuration for the Makerparts 3D printer (www.makerparts.net)

* Tuned MakerParts acceleration on X and Y axis so it never loses steps. Also adjusted pulses per mm to match default hw configuration

* Fine tuned Maximum acceleration for MakerParts printer

* Style cleanup

* Style changes to u8g_dev_st7920_128_64_sw_spi.cpp

* Even more improvements to the FastIO HAL for DUE. Now WRITE() is 2 ASM instructions, if value is constant, and 5 cycles if value is not constant. Previously, it was 7..8 cycles

* After some problems and debugging, seems we need to align the interrupt vector table to 256 bytes, otherwise, the program sometimes stops working

* Moved comments out of macro, otherwise, token pasting does not properly work sometimes

* Improved Software SPI implementation on DUE: Now it honors the selected speed passed to spiInit(). This allows much faster SDCARD access, improving SDCARD menus and reducing latency

* Update u8g_dev_st7920_128_64_sw_spi.cpp

* Disabling EEPROM over FLASH emulatiion if an I2C or SPI EEPROM is present

From @ejtagle, originally #7459

Implement AVR Platform

* [New Feature] I2C position encoder support

I plan to continue improving/cleaning this up, as there areas that need work.

* let the cleanups begin.

* progress

* more progress

* comments, rename files, etc.

* clean

* Cleanups per thinkyhead

* a few more cleanups

* cleanups, bugfixes, etc.

* remove unnecessary passes_test(), additional cleanups/optimizations

* cleanups

* misc.

* Fix up I2CPEM.init() and a few other things.

* organize, fix, rename, etc.

* more optimization

* a few more tweaks

* UBL G29 -P3.1 mesh fill with distance-weighted least squares fit.

* Back to original -O0 on G29 for now.

Rather than include twice, which is tricky but may confuse

This is the easiest way to make button pin testing consistent without
renaming all the button pins. Just make a macro especially for testing
if button pins are set, since they are named consistently in the pins
files.