Cleanup warnings

.travis.yml

Marlin/src/HAL/HAL_LPC1768/HAL_spi.cpp

Marlin/src/HAL/HAL_LPC1768/HardwareSerial.cpp

Marlin/src/HAL/HAL_LPC1768/LPC1768_Servo.cpp

Marlin/src/HAL/HAL_LPC1768/SoftwareSerial.cpp

Marlin/src/HAL/HAL_LPC1768/SoftwareSerial.h

Marlin/src/HAL/HAL_LPC1768/arduino.cpp

Marlin/src/feature/mixing.cpp

Marlin/src/feature/pause.cpp

Marlin/src/gcode/calibrate/M100.cpp

Marlin/src/gcode/config/M43.cpp

Marlin/src/gcode/feature/pause/M125.cpp

Marlin/src/gcode/gcode.cpp

Marlin/src/gcode/parser.cpp

Marlin/src/lcd/ultralcd.cpp

Marlin/src/libs/hex_print_routines.cpp

Marlin/src/libs/nozzle.cpp

Marlin/src/module/stepper.cpp

Marlin/src/module/temperature.cpp

Marlin/src/module/tool_change.cpp