Handle the -batch option centrally in cmdline.c.

This removes one case from several of the individual tools'
command-line parsers, and moves it into a central place where it will
automatically be supported by any tool containing console.c.

In order to make that not cause a link failure, there's now a
stubs/no-console.c which GUI clients of cmdline.c must include.

console.c

@@ -36,6 +36,12 @@ const SeatDialogPromptDescriptions *console_prompt_descriptions(Seat *seat)
 
 bool console_batch_mode = false;
 
+bool console_set_batch_mode(bool newvalue)
+{
+    console_batch_mode = newvalue;
+    return true;
+}
+
 /*
  * Error message and/or fatal exit functions, all based on
  * console_print_error_msg which the platform front end provides.