esp8266/Makefile: Document "disable" value for UART_OS.
esp8266/Makefile: Document "disable" value for UART_OS.

cwyark/micropython,chrisdearman/micropython,ryannathans/micropython,adafruit/micropython,pfalcon/micropython,bvernoux/micropython,mpalomer/micropython,toolmacher/micropython,AriZuu/micropython,torwag/micropython,toolmacher/micropython,tuc-osg/micropython,mpalomer/micropython,PappaPeppar/micropython,redbear/micropython,adafruit/micropython,AriZuu/micropython,MrSurly/micropython,turbinenreiter/micropython,AriZuu/micropython,adafruit/micropython,lowRISC/micropython,TDAbboud/micropython,lowRISC/micropython,pozetroninc/micropython,tuc-osg/micropython,dmazzella/micropython,ryannathans/micropython,adafruit/circuitpython,torwag/micropython,alex-robbins/micropython,torwag/micropython,swegener/micropython,MrSurly/micropython-esp32,henriknelson/micropython,hiway/micropython,hiway/micropython,oopy/micropython,henriknelson/micropython,hosaka/micropython,jmarcelino/pycom-micropython,dxxb/micropython,deshipu/micropython,hosaka/micropython,Peetz0r/micropython-esp32,dxxb/micropython,Peetz0r/micropython-esp32,tobbad/micropython,HenrikSolver/micropython,SHA2017-badge/micropython-esp32,adafruit/circuitpython,trezor/micropython,tuc-osg/micropython,tobbad/micropython,emfcamp/micropython,Timmenem/micropython,PappaPeppar/micropython,AriZuu/micropython,tralamazza/micropython,cwyark/micropython,torwag/micropython,henriknelson/micropython,puuu/micropython,blazewicz/micropython,bvernoux/micropython,dinau/micropython,jmarcelino/pycom-micropython,MrSurly/micropython-esp32,dinau/micropython,dxxb/micropython,blazewicz/micropython,kerneltask/micropython,tobbad/micropython,micropython/micropython-esp32,deshipu/micropython,pfalcon/micropython,pfalcon/micropython,bvernoux/micropython,hiway/micropython,cwyark/micropython,MrSurly/micropython,trezor/micropython,pramasoul/micropython,tralamazza/micropython,ryannathans/micropython,puuu/micropython,jmarcelino/pycom-micropython,SHA2017-badge/micropython-esp32,PappaPeppar/micropython,MrSurly/micropython-esp32,oopy/micropython,matthewelse/micropython,infinnovation/micropython,chrisdearman/micropython,swegener/micropython,MrSurly/micropython,chrisdearman/micropython,alex-march/micropython,PappaPeppar/micropython,oopy/micropython,dinau/micropython,lowRISC/micropython,tobbad/micropython,ryannathans/micropython,AriZuu/micropython,adafruit/micropython,alex-march/micropython,mhoffma/micropython,Timmenem/micropython,toolmacher/micropython,alex-robbins/micropython,adafruit/circuitpython,puuu/micropython,dmazzella/micropython,HenrikSolver/micropython,dmazzella/micropython,puuu/micropython,deshipu/micropython,deshipu/micropython,toolmacher/micropython,matthewelse/micropython,redbear/micropython,HenrikSolver/micropython,mpalomer/micropython,TDAbboud/micropython,Peetz0r/micropython-esp32,pozetroninc/micropython,deshipu/micropython,micropython/micropython-esp32,hosaka/micropython,mhoffma/micropython,HenrikSolver/micropython,adafruit/micropython,dmazzella/micropython,oopy/micropython,mhoffma/micropython,Peetz0r/micropython-esp32,mpalomer/micropython,pramasoul/micropython,SHA2017-badge/micropython-esp32,kerneltask/micropython,bvernoux/micropython,Timmenem/micropython,chrisdearman/micropython,alex-robbins/micropython,toolmacher/micropython,micropython/micropython-esp32,MrSurly/micropython,pramasoul/micropython,torwag/micropython,selste/micropython,selste/micropython,trezor/micropython,matthewelse/micropython,alex-robbins/micropython,cwyark/micropython,matthewelse/micropython,mhoffma/micropython,turbinenreiter/micropython,kerneltask/micropython,pfalcon/micropython,MrSurly/micropython,SHA2017-badge/micropython-esp32,MrSurly/micropython-esp32,pfalcon/micropython,kerneltask/micropython,MrSurly/micropython-esp32,jmarcelino/pycom-micropython,blazewicz/micropython,emfcamp/micropython,pramasoul/micropython,swegener/micropython,adafruit/circuitpython,alex-robbins/micropython,pozetroninc/micropython,adafruit/circuitpython,micropython/micropython-esp32,mhoffma/micropython,Timmenem/micropython,emfcamp/micropython,chrisdearman/micropython,ganshun666/micropython,henriknelson/micropython,tuc-osg/micropython,redbear/micropython,mpalomer/micropython,matthewelse/micropython,turbinenreiter/micropython,turbinenreiter/micropython,ganshun666/micropython,PappaPeppar/micropython,ganshun666/micropython,TDAbboud/micropython,kerneltask/micropython,bvernoux/micropython,ryannathans/micropython,dinau/micropython,emfcamp/micropython,micropython/micropython-esp32,alex-march/micropython,trezor/micropython,pozetroninc/micropython,hosaka/micropython,lowRISC/micropython,oopy/micropython,selste/micropython,tuc-osg/micropython,HenrikSolver/micropython,alex-march/micropython,emfcamp/micropython,lowRISC/micropython,adafruit/circuitpython,matthewelse/micropython,tralamazza/micropython,blazewicz/micropython,infinnovation/micropython,dxxb/micropython,redbear/micropython,SHA2017-badge/micropython-esp32,ganshun666/micropython,selste/micropython,hiway/micropython,cwyark/micropython,pramasoul/micropython,TDAbboud/micropython,Timmenem/micropython,puuu/micropython,turbinenreiter/micropython,pozetroninc/micropython,tobbad/micropython,hiway/micropython,jmarcelino/pycom-micropython,ganshun666/micropython,swegener/micropython,Peetz0r/micropython-esp32,TDAbboud/micropython,redbear/micropython,selste/micropython,infinnovation/micropython,dinau/micropython,henriknelson/micropython,swegener/micropython,alex-march/micropython,infinnovation/micropython,blazewicz/micropython,dxxb/micropython,trezor/micropython,hosaka/micropython,tralamazza/micropython,infinnovation/micropython