Works around PIO src_filter behavior (see https://github.com/platformio/platformio-core/issues/1905)

need to identify why incompatible libraries are still included without specifically disallowing them

* Add traceback after watchdog timeout

Add the cpability to perform a traceback following a watchdog timeout.

* Enhanced hardware SPI

Allow use of either SSP0 or SSP1.
Ensure that no data is left in I/O buffers after calls to enable sharing of SSP hardware.

* Make flash emulation of eeprom the default

Make use of flash for eeprom storage the default. This means that usage of eeprom will not cause USB drive mount/unmount operations.

* Allow sharing of SD card

SD card I/O operations from the USB stack take place in idle loop, rather than at interrupt time. Allowing sharing of the SPI bus.

New configuration options to allow usage of the SD card to be specified.

* Fix problem with hardware SPI pins

Framework and build platform now located at https://github.com/p3p/pio-framework-arduino-lpc176x and https://github.com/p3p/pio-nxplpc-arduino-lpc176x respectively

fix mkssbase leds

move hardware serial

remove hardware/software serial

Hardware Serial extraction

HardwareSerial ISRs

fix disabled serial2 causing Serial object to link

move usb devices out to framework

separate out adc/pwm peripheral function from hal.cpp

fix includes

remove unused pwm init

move adc

HAL header update

templated filtered adc

LPC1769 platform

I missed this one

This reverts commit 77efcad1.

-normalize `env` and `board` to lowercase naming convention.
-make board `name` follow descriptive convention.
-implement `-fsingle-precision-constant` compile optimization per https://github.com/MarlinFirmware/Marlin/pull/11178#issuecomment-401673901
-fix typo in 5DPRINT entry.

This reverts commit a26fdf6b.

On a leap of faith...  I'm merging...

See https://github.com/MarlinFirmware/Marlin/pull/11079#issuecomment-399309709

-Enable boards_dir option in PIO INI
-Remove defunct custom board file operations for PIO auto-build environment
-Remove now-defunct Teensy++ 2.0 PIO entry, replaced by `at90USB1286_DFU` and `at90USB1286_DFU` (using this entry always put AT90USB board boot loaders in jeopardy of being overwritten due to the very small size of the official Teensy++ 2.0 bootloader)
-whitespace