initial ntp feature

This one has been partially implemented for regular builds
but making it generally available seems much better.

features.in/ntp/README

@@ -0,0 +1,4 @@
+Эта фича конфигурирует службу NTP в качестве клиента
+с целью предоставления точного времени в составе LiveCD;
+для установленных систем рекомендуется применение модуля
+alterator-datetime.

features.in/ntp/config.mk

@@ -0,0 +1,8 @@
+use/ntp: use/services
+	@$(call add_feature)
+	@$(call add,THE_PACKAGES,openntpd)
+	@$(call add,DEFAULT_SERVICES_ENABLE,ntpd)
+
+use/ntp/client: use/ntp
+	@$(call add,NTP_SERVERS,pool.ntp.org)
+	@$(call xport,NTP_SERVERS)

features.in/ntp/rootfs/image-scripts.d/50-ntp

@@ -0,0 +1,10 @@
+#!/bin/sh
+# basic NTP client configuration
+
+. shell-config
+
+CONFIG="/etc/ntpd.conf"
+[ -f "$CONFIG" ] || exit 0
+[ -n "$GLOBAL_NTP_SERVERS" ] || exit 0
+
+shell_config_set "$CONFIG" 'servers' "$GLOBAL_NTP_SERVERS" '[[:space:]]\+' ' '