f_swapfs, f_move_itable, f_resize_inode, test_config:
Allow the diff options to be set in test_config so that
diff -u can be used on platforms that have it. (To be
done: checking whether diff can support -u in the
configure script.)
for compatibility with FreeBSD. In $DEBUGFS commands, move the
-R arg argument first so that systems with non-GNU getopt()
can see the request argument (they would otherwise stop
parsing at the first non-option argument).