Make add_vlan and add_rtadv public commands.

rc.subr

@@ -177,7 +177,7 @@ _compute_nets()
     done
 }
 
-_add_vlan()
+add_vlan()
 {
     _card=$1
     _vlan=$2
@@ -201,7 +201,7 @@ _add_vlan()
     fi
 }
 
-_add_rtadv()
+add_rtadv()
 {
     _card=$1
     _vlan=$2
@@ -459,7 +459,7 @@ _emit_dhcpv4()
 add_v4_net()
 {
     _compute_nets $*
-    _add_vlan $_card $_vlan
+    add_vlan $_card $_vlan
 
     _class_group=""
     if [ ! -z "${_class}" ]
@@ -487,8 +487,8 @@ add_v6_net()
 {
 	_isp=""
     _compute_nets $*
-    _add_vlan $_card $_vlan
-    _add_rtadv $_card $_vlan
+    add_vlan $_card $_vlan
+    add_rtadv $_card $_vlan
 
 	_compute_ula_prefix