Support --mkconfig option

When invoked with --mkconfig <conf_file>, the options are stored in
conf_file and create_ap exits.

bash_completion

@@ -2,6 +2,14 @@
 # Bash Completion routine for create_ap
 #
 
+_use_filedir() {
+    if [[ $(type -t _filedir) == "function" ]]; then
+        _filedir
+        return 0
+    fi
+    return 1
+}
+
 _create_ap() {
     local awk_cmd='
         ($1 ~ /^-/) {
@@ -117,6 +125,9 @@ _create_ap() {
         --list)
             # No Options
             ;;
+        --mkconfig)
+            _use_filedir && return 0
+            ;;
         -g)
             # Not going to implement
             ;;