Add TZ.h database, borrowed from ESP8266 core (#1947)

tools/tzupdate.sh

+#!/bin/sh
+
+# this shell script refreshes world timezone definitions in
+#   cores/rp2040/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 > $input
+
+sed -e 's/^[^,]*,//g' -e 's,^,(,g' -e 's,$,),g' < $input > $values
+sed -e 's/^\([^,]*\),.*/#define TZ_\1/g' -e 's,["],,g' < $input | tr '/\-+' '_mp' > $names
+
+(
+
+cat << EOF
+
+// autogenerated from $csv
+// by script <rp2040 arduino core>/tools/${base}
+// $(date -u)
+//
+// This database is autogenerated from IANA timezone database
+//    ${csv}
+//    (using https://www.iana.org/time-zones)
+// and can be updated on demand in this repository
+// or by yourself using the above script
+
+#pragma once
+
+EOF
+
+paste $names $values
+
+) > $tz_tmpdir/TZ.h
+
+backup=$(date +%s)
+mv ${dir}/../cores/rp2040/TZ.h ${dir}/../cores/rp2040/TZ.h.$backup
+mv $tz_tmpdir/TZ.h ${dir}/../cores/rp2040/TZ.h
+
+cat << EOF
+
+Done:
+    '${dir}/../cores/rp2040/TZ.h' is updated
+
+Diff:
+----8<-------8<------8<---
+$(diff -u ${dir}/../cores/rp2040/TZ.h.$backup ${dir}/../cores/rp2040/TZ.h)
+--->8----->8------>8------
+
+EOF