01443a9619
1. Turn off MICROPY_CPYTHON_COMPAT, which includes a number of minor CPython compatibility features, most of which have workarounds, but uses up significant flash. 2. Turn on MICROPY_PY_SYS_MAXSIZE, which implements sys.maxsize. 3. Turn on MICROPY_CAN_OVERRIDE_BUILTINS, which implements "_" as the most recent value in the REPL, and also enables redefining builtins.