Merge branch 'feature/deep_sleep_wakeup_from_touch' into 'master'

add wakeup from touch sensor, and deep sleep example

- add new deep sleep wakeup mode
- change documentation to explain incompatibilities between different wakeup mode, add error checks
- add new ULP instructions necessary for ULP wakeup scenario
- fix issues with I_WR_REG, I_SLEEP, I_END instructions
- add deep sleep example, illustrating the use of timer, gpio, touch, and ULP wakeup triggers

See merge request !461

components/newlib/time.c

@@ -52,7 +52,7 @@ static uint64_t get_rtc_time_us()
     uint64_t low = READ_PERI_REG(RTC_CNTL_TIME0_REG);
     uint64_t high = READ_PERI_REG(RTC_CNTL_TIME1_REG);
     uint64_t ticks = (high << 32) | low;
-    return ticks * 100 / (RTC_CTNL_SLOWCLK_FREQ / 10000);    // scale RTC_CTNL_SLOWCLK_FREQ to avoid overflow
+    return ticks * 100 / (RTC_CNTL_SLOWCLK_FREQ / 10000);    // scale RTC_CNTL_SLOWCLK_FREQ to avoid overflow
 }
 #endif // WITH_RTC