* pmsleep refactor
* Shortened swtmr disabled message
* Added swtimer debug module option to user_modules.h.
* Added comments to user_config.h.
* Fixed error in documentation for node.sleep()
* remove blank sntp.c that got added in during rebase onto dev(6218b92)
* Added #ifdefs around SWTIMER_REG_CB to prevent inclusion of disabled
code
* Change upper limit for timer in `tmr_register` and `tmr_interval` to reflect new limit in SDK 1.5.3.
* Change documentation for `tmr.alarm()`, `tmr.interval()` and `tmr.register()` to match source.
* Improve error reporting to be more descriptive.
Module creation & registration now made a lot simpler. In essence,
each module file is now self-contained and only needs a
NODEMCU_MODULE(MYNAME, "myname", myname_map, luaopen_myname);
line to both be automatically recognised by the Lua initialization
as well as honor the LUA_USE_MODULES_MYNAME #define.
As per #810 & #796, only LUA_OPTIMIZE_MEMORY=2 & MIN_OPT_LEVEL=2 are
supported when building. This commit effects that limitation.
With this change modules/auxmods.h no longer needs to be updated for
every new module, nor do module writers need to cater for a hypothetical
LUA_OPTIMIZE_MEMORY < 2 scenario.
With the new SDK soft-wdt it is no longer sufficient to tickle the hardware
watchdog, so all (found) instances have been changed to system_soft_wdt_feed().