lib/lwip: Update lwIP to v2.0.3, tag STABLE-2_0_3_RELEASE.
lib/lwip: Update lwIP to v2.0.3, tag STABLE-2_0_3_RELEASE.

bvernoux/micropython,dmazzella/micropython,pozetroninc/micropython,henriknelson/micropython,adafruit/micropython,adafruit/micropython,selste/micropython,tobbad/micropython,pfalcon/micropython,pfalcon/micropython,swegener/micropython,swegener/micropython,bvernoux/micropython,tralamazza/micropython,MrSurly/micropython,swegener/micropython,bvernoux/micropython,pozetroninc/micropython,tobbad/micropython,adafruit/circuitpython,MrSurly/micropython,kerneltask/micropython,MrSurly/micropython,trezor/micropython,henriknelson/micropython,tobbad/micropython,kerneltask/micropython,selste/micropython,adafruit/circuitpython,pramasoul/micropython,tralamazza/micropython,tralamazza/micropython,selste/micropython,adafruit/micropython,dmazzella/micropython,kerneltask/micropython,trezor/micropython,kerneltask/micropython,pramasoul/micropython,dmazzella/micropython,MrSurly/micropython,MrSurly/micropython,tobbad/micropython,henriknelson/micropython,pfalcon/micropython,pfalcon/micropython,adafruit/micropython,pramasoul/micropython,bvernoux/micropython,pfalcon/micropython,pozetroninc/micropython,tralamazza/micropython,adafruit/circuitpython,trezor/micropython,tobbad/micropython,pramasoul/micropython,swegener/micropython,swegener/micropython,pramasoul/micropython,trezor/micropython,pozetroninc/micropython,trezor/micropython,selste/micropython,selste/micropython,dmazzella/micropython,adafruit/micropython,adafruit/circuitpython,adafruit/circuitpython,henriknelson/micropython,kerneltask/micropython,henriknelson/micropython,bvernoux/micropython,adafruit/circuitpython,pozetroninc/micropython