Updated partition offset wike about GRUB experiment

doc/partition_offset.wiki

@@ -104,10 +104,42 @@ cutting off the first partition_offset blocks of 2 KB:
 
 --------------------------------------------------------------------------
 
+Another test was made with GRUB 2 by downloading
+{{{
+  bzr branch http://bzr.savannah.gnu.org/r/grub/trunk/grub
+}}}
+
+Before building GRUB 2, the file
+{{{
+  util/grub-mkrescue.in
+}}}
+was edited to replace in the options of the xorriso command:
+{{{
+  --protective-msdos-label
+}}}
+by
+{{{
+  -partition_offset 16 -no-pad --no-emul-toc
+}}}
+Then GRUB 2 was built and installed.
+
+The resulting image from
+{{{
+  ./grub-mkrescue -o image.iso
+}}}
+was put onto USB stick. It passed the same tests on Debian
+as above RIPLinux example. It boots to a GRUB prompt.
+
+Due to options -no-pad --no-emul-toc the image is about 300 kB smaller than
+the image produced by original grub-mkrescue. Else it would have grown by
+about 130 kB.
+
+--------------------------------------------------------------------------
+
 Open questions:
 
 - Shall the partition of an isohybrid image be marked bootable ?
-  Currently xorriso keeps the 0x80 mark of an eventually imported MBR
+Currently xorriso keeps the 0x80 mark of an eventually imported MBR
 resp. the 0x80 mark which xorriso eventually sets by its own MBR
 preparations.
   - If not to be marked bootable: