unix/mpconfigport.h: Enable MICROPY_PY_DELATTR_SETATTR.
unix/mpconfigport.h: Enable MICROPY_PY_DELATTR_SETATTR.

This is a generally useful feature and because it's part of the object
model it cannot be added at runtime by some loadable Python code, so enable
it on the standard unix build.

bvernoux/micropython,MrSurly/micropython,henriknelson/micropython,bvernoux/micropython,henriknelson/micropython,bvernoux/micropython,adafruit/circuitpython,bvernoux/micropython,adafruit/circuitpython,henriknelson/micropython,MrSurly/micropython,MrSurly/micropython,henriknelson/micropython,adafruit/circuitpython,bvernoux/micropython,adafruit/circuitpython,henriknelson/micropython,adafruit/circuitpython,adafruit/circuitpython,MrSurly/micropython,MrSurly/micropython