Improve RPi detection

- Add check for 64-bit versions of Raspberry Pi OS, e.g. Ubuntu 20.04
  on Raspberry Pi 4
- Ref: #852

extras/ikev2setup.sh

@@ -320,7 +320,7 @@ case "$swan_ver" in
     ;;
 esac
 
-if uname -m | grep -qi '^arm'; then
+if uname -m | grep -qi -e '^arm' -e '^aarch64'; then
   mobike_support=0
 fi
 

vpnsetup.sh

@@ -76,7 +76,7 @@ def_iface=$(route 2>/dev/null | grep -m 1 '^default' | grep -o '[^ ]*$')
 [ -z "$def_iface" ] && def_iface=$(ip -4 route list 0/0 2>/dev/null | grep -m 1 -Po '(?<=dev )(\S+)')
 def_state=$(cat "/sys/class/net/$def_iface/operstate" 2>/dev/null)
 if [ -n "$def_state" ] && [ "$def_state" != "down" ]; then
-  if ! uname -m | grep -qi '^arm'; then
+  if ! uname -m | grep -qi -e '^arm' -e '^aarch64'; then
     case "$def_iface" in
       wl*)
         exiterr "Wireless interface '$def_iface' detected. DO NOT run this script on your PC or Mac!"