Add support for pre/ap-pended original DNS servers.

--- ./vpnc-script	2016-08-28 08:27:51.000000000 +0200
+++ /etc/vpnc/vpnc-script	2016-11-19 22:21:39.427685497 +0100
@@ -81,6 +81,10 @@
 DEFAULT_ROUTE_FILE=/var/run/vpnc/defaultroute
 RESOLV_CONF_BACKUP=/var/run/vpnc/resolv.conf-backup
 SCRIPTNAME=`basename $0`
+
+# Valid values are "before" and "after", to pre/ap-pend your nameservers
+# compared to VPN ones3. You can use the hooks support to configure this.
+KEEP_ORIGINAL_DNS="no"
 
 # some systems, eg. Darwin & FreeBSD, prune /var/run on boot
 if [ ! -d "/var/run/vpnc" ]; then
@@ -370,12 +371,13 @@
 # as long as the above mark is intact"
 
 	DOMAINS="$CISCO_DEF_DOMAIN"
+	ORIGINAL_IP4_DNS=""
 
 	exec 6< "$RESOLV_CONF_BACKUP"
 	while read LINE <&6 ; do
 		case "$LINE" in
 			# omit; we will overwrite these
-			nameserver*) ;;
+			nameserver*) ORIGINAL_IP4_DNS="${LINE#* } $ORIGINAL_IP4_DNS" ;;
 			# extract listed domains and prepend to list
 			domain* | search*) DOMAINS="${LINE#* } $DOMAINS" ;;
 			# retain other lines
@@ -385,10 +387,21 @@
 	done
 	exec 6<&-
 
+	[ "${KEEP_ORIGINAL_DNS}" = before ] && \
+	for i in $ORIGINAL_IP4_DNS ; do
+		NEW_RESOLVCONF="$NEW_RESOLVCONF
+nameserver $i"
+	done
 	for i in $INTERNAL_IP4_DNS ; do
 		NEW_RESOLVCONF="$NEW_RESOLVCONF
 nameserver $i"
 	done
+	[ "${KEEP_ORIGINAL_DNS}" = after ] && \
+	for i in $ORIGINAL_IP4_DNS ; do
+		NEW_RESOLVCONF="$NEW_RESOLVCONF
+nameserver $i"
+	done
+
 	# note that "search" is mutually exclusive with "domain";
 	# "search" allows multiple domains to be listed, so use that
 	if [ -n "$DOMAINS" ]; then