Add 'xdiff/' from commit '0938805d00020fed3782623d424772ff8b36fcc6'

git-subtree-dir: xdiff
git-subtree-mainline: 9bc1b635a5db922eaff66a71afb7c7f6f4230b8a
git-subtree-split: 0938805d00020fed3782623d424772ff8b36fcc6