PsychLinuxConfiguration: Handle xorg.conf.dir on RaspberryPi OS 12.

RaspberryPiOS 12 can create its own /etc/X11/xorg.conf.dir/ - owned by
user and group root, to store config files specific to RPi4+. In that
case, our detection of "missing xorg.conf.dir" skipped, as the dir was
there, but then group ownership of the dir was by root, not by our group
psychtoolbox, therefore it was not writable by XOrgConfSelector.

Be more clever and handle the case of an existing dir with wrong group
ownership, and in that case, just offer to change group ownership to
psychtoolbox, with suitable write permissions.

-> Should fix failure of XOrgConfSelector() on RaspberryPi OS 12+

Psychtoolbox/PsychLinuxConfiguration.m

@@ -558,17 +558,35 @@
 end
 
 if addgroup
-  if ~exist('/etc/X11/xorg.conf.d', 'dir')
-    fprintf('\n\nThe X11 configuration directory /etc/X11/xorg.conf.d does not exist.\n');
-    fprintf('I would like to create it and allow users of the psychtoolbox Unix group\n');
+  % Check if xorg.conf.d exists, but does not have psychtoolbox as owning group.
+  % In that case we need to chown + chmod it to ownership and write permission for
+  % psychtoolbox group. This happens, e.g., on RaspberryPi OS 12, when the system
+  % by itself creates the directory to place some config files, but not with psychtoolbox
+  % ownership. Need different ls() output string handling for Octave vs. Matlab for this:
+  if IsOctave
+    xorgconfdir = vec(ls('/etc/X11/', '-l')')';
+  else
+    xorgconfdir = ls('/etc/X11/', '-l');
+  end
+  xorgnotptbowned = exist('/etc/X11/xorg.conf.d', 'dir') && isempty(strfind(xorgconfdir, 'psychtoolbox'));
+
+  % Does not exist or is not group owned by us?
+  if ~exist('/etc/X11/xorg.conf.d', 'dir') || xorgnotptbowned
+    if xorgnotptbowned
+      fprintf('\n\nThe X11 configuration directory /etc/X11/xorg.conf.d is not owned by\n');
+      fprintf('the psychtoolbox Unix group. I would like to change that, to allow you\n');
+    else
+      fprintf('\n\nThe X11 configuration directory /etc/X11/xorg.conf.d does not exist.\n');
+      fprintf('I would like to create it and allow users of the psychtoolbox Unix group\n');
+    end
     fprintf('to write xorg config files into that directory. This will allow easy change\n');
     fprintf('of display configuration when needed to setup for an experiment by use of the\n');
     fprintf('XOrgConfCreator and XOrgConfSelector functions of Psychtoolbox.\n\n');
 
     if ismember(answers(4), 'yn')
       answer = answers(4);
     else
-      answer = input('Should i create a X11 config directory that is writable for you? [y/n] : ', 's');
+      answer = input('Should i create or configure a X11 config directory that is writable for you? [y/n] : ', 's');
       answers(4) = answer;
     end
 
@@ -580,7 +598,9 @@
         fprintf('GUI, e.g., via executing: octave --no-gui\n');
         fprintf('Then run the PsychLinuxConfiguration command again to make things work.\n');
       else
-        system('sudo mkdir /etc/X11/xorg.conf.d');
+        if ~exist('/etc/X11/xorg.conf.d', 'dir')
+          system('sudo mkdir /etc/X11/xorg.conf.d');
+        end
         system('sudo chown :psychtoolbox /etc/X11/xorg.conf.d');
         system('sudo chmod g+rwxs /etc/X11/xorg.conf.d');
       end