Fix default interface bindings (fourth time)

The following changes introduced in Bash 4.3 necessitate this commit:
- Setting the array attribute no longer initializes an array.
- Empty-but-set arrays no longer pass [[ -v ]].

Previous attempts:
feb669f
711c464
e821082

src/lib/connections/bond

@@ -2,7 +2,8 @@
 
 . "$SUBR_DIR/ip"
 
-declare -ag BindsToInterfaces
+# Make sure BindsToInterfaces is set
+BindsToInterfaces=("${BindsToInterfaces[@]}")
 
 bond_up() {
     if is_interface "$Interface"; then

src/lib/connections/bridge

@@ -2,7 +2,8 @@
 
 . "$SUBR_DIR/ip"
 
-declare -ag BindsToInterfaces
+# Make sure BindsToInterfaces is set
+BindsToInterfaces=("${BindsToInterfaces[@]}")
 
 bridge_up() {
     if is_interface "$Interface"; then

src/lib/connections/dummy

@@ -2,7 +2,8 @@
 
 . "$SUBR_DIR/ip"
 
-declare -ag BindsToInterfaces
+# Make sure BindsToInterfaces is set
+BindsToInterfaces=("${BindsToInterfaces[@]}")
 
 dummy_up() {
     if is_interface "$Interface"; then

src/lib/connections/tunnel

@@ -2,7 +2,8 @@
 
 . "$SUBR_DIR/ip"
 
-declare -ag BindsToInterfaces
+# Make sure BindsToInterfaces is set
+BindsToInterfaces=("${BindsToInterfaces[@]}")
 
 tunnel_up() {
     if is_interface "$Interface"; then

src/lib/connections/tuntap

@@ -2,7 +2,8 @@
 
 . "$SUBR_DIR/ip"
 
-declare -ag BindsToInterfaces
+# Make sure BindsToInterfaces is set
+BindsToInterfaces=("${BindsToInterfaces[@]}")
 
 tuntap_up() {
     if is_interface "$Interface"; then

src/netctl.in

@@ -111,7 +111,7 @@ unit_enable() {
     echo ".include @systemdsystemunitdir@/netctl@.service" > "$unit"
     echo -e "\n[Unit]" >> "$unit"
     [[ -n $Description ]] && echo "Description=$Description" >> "$unit"
-    [[ -v BindsToInterfaces ]] || BindsToInterfaces=$Interface
+    declare -p BindsToInterfaces &> /dev/null || BindsToInterfaces=$Interface
     if (( ${#BindsToInterfaces[@]} )); then
         : ${InterfaceRoot=sys/subsystem/net/devices/}
         printf "BindsTo=$(sd_escape "$InterfaceRoot")%s.device\n" \