Official support for low power modes

[pythoncoder]

Currently the only officially supported way to recover from the "deep sleep" mode is rtc.wakeup(). I have a module upower.py documented here https://github.com/peterhinch/micropyth ... opower.git. It uses the stm module to enable waking by means of RTC alarms and pin changes on the two available pins. It provides other functionality relevant to low power operation including access to the backup RAM and RTC registers and a low power version of pyb.delay(). The code is currently a hack, but could be made standards-compliant if there's any interest in an official Python module.

Or is the plan to support this functionality in firmware? I'd be happy to offer a module for review in the New Year if Python/stm is the preferred solution.