add a list append function to functions.sh

git-svn-id: svn://svn.openwrt.org/openwrt/branches/buildroot-ng/openwrt@4014 3c298f89-4303-0410-b956-a3cf2f4a3e73

package/base-files/default/etc/functions.sh

@@ -1,6 +1,10 @@
 #!/bin/sh
 alias debug=${DEBUG:-:}
 
+# newline
+N="
+"
+
 # valid interface?
 if_valid () (
   ifconfig "$1" >&- 2>&- ||
@@ -12,6 +16,13 @@ hotplug_dev() {
 	env -i ACTION=$1 INTERFACE=$2 /sbin/hotplug net
 }
 
+append() {
+	local var="$1"
+	local value="$2"
+	local sep="${3:- }"
+	eval "export ${var}=\"\${${var}:+\${${var}}${value:+$sep}}$value\""
+}
+
 config_cb() {
 	return 0
 }