* Make the rtc variables not be cleared by the .bss initialization
* Move the save to the right place
* Make sure that we reset the rtctime to 0 if we didn't sleep properly.
* Setting the seconds to zero doesn't update the dsleep calibration
* Improve RTC timekeeping -- includes clock rate tracking
* Improved division by 1M
* Fix crash in sntp
* Disable RTC debug
* Get the offset correct
* Add comments on where the mysterious numbers came from
* Fix a crash with auto repeat mode and errors on repeat
* Switch off interrupts before rtctime dsleep.
* Deal with the fact that MCU keeps running after being told to enter deep sleep
(It can keep running for quite a few instructions at times (and none at
all at others), and it appears that trying to cache additional code from
SPI flash while trying to go to sleep fails miserably at both....)
* Ensure flash is not active when going into deep sleep.
Philip Gladstone
Johny Mattsson
Johny Mattsson