py/formatfloat: Use standard isinf, isnan funcs instead of custom ones.
py/formatfloat: Use standard isinf, isnan funcs instead of custom ones.

Reduces code size by a tiny bit.

tralamazza/micropython,tralamazza/micropython,tobbad/micropython,MrSurly/micropython-esp32,AriZuu/micropython,swegener/micropython,tobbad/micropython,kerneltask/micropython,torwag/micropython,trezor/micropython,blazewicz/micropython,kerneltask/micropython,trezor/micropython,pramasoul/micropython,blazewicz/micropython,pfalcon/micropython,MrSurly/micropython,pozetroninc/micropython,micropython/micropython-esp32,adafruit/circuitpython,infinnovation/micropython,dmazzella/micropython,bvernoux/micropython,MrSurly/micropython-esp32,pramasoul/micropython,infinnovation/micropython,micropython/micropython-esp32,MrSurly/micropython,micropython/micropython-esp32,MrSurly/micropython,MrSurly/micropython-esp32,bvernoux/micropython,AriZuu/micropython,pramasoul/micropython,bvernoux/micropython,tobbad/micropython,swegener/micropython,lowRISC/micropython,dmazzella/micropython,trezor/micropython,selste/micropython,MrSurly/micropython,selste/micropython,MrSurly/micropython-esp32,torwag/micropython,pozetroninc/micropython,pfalcon/micropython,pozetroninc/micropython,trezor/micropython,pramasoul/micropython,infinnovation/micropython,tralamazza/micropython,torwag/micropython,MrSurly/micropython,selste/micropython,pfalcon/micropython,torwag/micropython,adafruit/circuitpython,blazewicz/micropython,ryannathans/micropython,MrSurly/micropython-esp32,trezor/micropython,tobbad/micropython,micropython/micropython-esp32,selste/micropython,pozetroninc/micropython,AriZuu/micropython,kerneltask/micropython,infinnovation/micropython,ryannathans/micropython,infinnovation/micropython,ryannathans/micropython,adafruit/circuitpython,lowRISC/micropython,henriknelson/micropython,ryannathans/micropython,dmazzella/micropython,pozetroninc/micropython,selste/micropython,kerneltask/micropython,adafruit/circuitpython,bvernoux/micropython,kerneltask/micropython,henriknelson/micropython,henriknelson/micropython,tralamazza/micropython,pfalcon/micropython,lowRISC/micropython,lowRISC/micropython,blazewicz/micropython,tobbad/micropython,ryannathans/micropython,swegener/micropython,torwag/micropython,pramasoul/micropython,henriknelson/micropython,swegener/micropython,adafruit/micropython,swegener/micropython,micropython/micropython-esp32,adafruit/circuitpython,blazewicz/micropython,AriZuu/micropython,dmazzella/micropython,lowRISC/micropython,adafruit/micropython,bvernoux/micropython,henriknelson/micropython,adafruit/circuitpython,pfalcon/micropython,AriZuu/micropython,adafruit/micropython,adafruit/micropython,adafruit/micropython