time: import IANA timezone definitions, expose SNTP API (#6373)

* time: import IANA timezone definitions
- `configTime("timezone", "ntp servers...")` added
- timezone definitions by country/cities (TZ.h)
- script to update timezone definitions
- updated example

* fix former configTime non-matching signature

* +include

* example: add scheduled function in callback

* crlf fix

* +missing license for napt

* SNTP: expose configuration helpers

* update submodule

* update precompiled libraries

* optional: change SNTP startup delay

* makes SNTP_UPDATE_DELAY a weak function
update example
fix for lwip1.4

* on the proper use of polledTimeout api... thanks @mcspr :]

* improve update script (per review)

* update lwIP submodule

* update submodule

* hide harmless shell message

* update the release process by asking first to update TZ.h
[ci skip]

* minor update in release documentation

* update in release documentation

* update in release documentation

* clarify release documentation

* fix release documentation - sorry for the noise :(

* fixes per review

* example style

* useless variable in example

* update lwip2 submodule reference, to include espressif missing declaration fixes

tools/TZupdate.sh

@@ -0,0 +1,71 @@
+#!/bin/sh
+
+# this shell script refreshes world timezone definitions in
+#   cores/esp8266/TZ.h
+#
+# to run it, use:
+#   /path/to/TZupdate.sh
+#   tools/TZupdate.sh
+#   ./TZupdate.sh
+
+dir=$(cd ${0%/*} 2>/dev/null; pwd)
+base=${0##*/}
+
+csv=https://raw.githubusercontent.com/nayarsystems/posix_tz_db/master/zones.csv
+
+set -e
+
+tz_tmpdir=$(mktemp -d)
+trap 'rm -r $tz_tmpdir' EXIT
+
+input=$tz_tmpdir/zones.csv
+names=$tz_tmpdir/names.txt
+values=$tz_tmpdir/values.txt
+
+wget -O $input $csv  || curl $csv > $input
+
+sed -e 's/^[^,]*,//g' -e 's,^,PSTR(,g' -e 's,$,),g' < $input > $values
+sed -e 's/^\([^,]*\),.*/#define TZ_\1/g' -e 's,["],,g' < $input | tr '/\-+' '_mp' > $names
+
+(
+
+cat << EOF
+
+// autogenerated from $csv
+// by script <esp8266 arduino core>/tools/${base}
+// $(date -u)
+//
+// This database is autogenerated from IANA timezone database
+//    https://www.iana.org/time-zones
+// and can be updated on demand in this repository
+// or by yourself using the above script
+
+#ifndef TZDB_H
+#define TZDB_H
+
+EOF
+
+paste $names $values
+
+cat << EOF
+
+#endif // TZDB_H
+EOF
+
+) > $tz_tmpdir/TZ.h
+
+backup=$(date +%s)
+mv ${dir}/../cores/esp8266/TZ.h ${dir}/../cores/esp8266/TZ.h.$backup
+mv $tz_tmpdir/TZ.h ${dir}/../cores/esp8266/TZ.h
+
+cat << EOF
+
+Done:
+    '${dir}/../cores/esp8266/TZ.h' is updated
+
+Diff:
+----8<-------8<------8<---
+$(diff -u ${dir}/../cores/esp8266/TZ.h.$backup ${dir}/../cores/esp8266/TZ.h)
+--->8----->8------>8------
+
+EOF