esp8266/posix_helpers: Set ENOMEM on memory alloc failure.
esp8266/posix_helpers: Set ENOMEM on memory alloc failure.

POSIX requires malloc(), etc. to set ENOMEM on the failure, and e.g.
BerkeleyDB relies on this:

http://pubs.opengroup.org/onlinepubs/9699919799/functions/malloc.html

This should fix confusing OSError exceptions with 0 error code when
working with btree module.

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