Although this is an external contribution, clean up anyway to stop seeing it in global searches for typical flaws.

* Enable hardware serial ports on LPC1768

* Fix compilation errors with other HALs

* FIx order of includes in LPC1768 HAL main.cpp

* Add support for RX_BUFFER_SIZE and TX_BUFFER_SIZE options in Configuration_adv.h

Fixes Arduino IDE builds for 8-bit AVR,
misc: Adafruit NeoPixel currently incompatible with Teensy 3.5-6, blacklisted