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

- TMC2130Stepper v2.2.0
- TMC2208Stepper v0.0.4

Followup to #10096