HAL for Linux (#13146)

.travis.yml

Marlin/src/HAL/HAL_LINUX/HAL.cpp

Marlin/src/HAL/HAL_LINUX/HAL.h

Marlin/src/HAL/HAL_LINUX/HAL_timers.cpp

Marlin/src/HAL/HAL_LINUX/HAL_timers.h

Marlin/src/HAL/HAL_LINUX/SanityCheck.h

Marlin/src/HAL/HAL_LINUX/arduino.cpp

Marlin/src/HAL/HAL_LINUX/fastio.h

Marlin/src/HAL/HAL_LINUX/hardware/Clock.cpp

Marlin/src/HAL/HAL_LINUX/hardware/Clock.h

Marlin/src/HAL/HAL_LINUX/hardware/Gpio.cpp

Marlin/src/HAL/HAL_LINUX/hardware/Gpio.h

Marlin/src/HAL/HAL_LINUX/hardware/Heater.cpp

Marlin/src/HAL/HAL_LINUX/hardware/Heater.h

Marlin/src/HAL/HAL_LINUX/hardware/IOLoggerCSV.cpp

Marlin/src/HAL/HAL_LINUX/hardware/IOLoggerCSV.h

Marlin/src/HAL/HAL_LINUX/hardware/LinearAxis.cpp

Marlin/src/HAL/HAL_LINUX/hardware/LinearAxis.h

Marlin/src/HAL/HAL_LINUX/hardware/Timer.cpp

Marlin/src/HAL/HAL_LINUX/hardware/Timer.h