Add 'xo-indentlog/' from commit 'd43c4af0b4'

git-subtree-dir: xo-indentlog
git-subtree-mainline: 1c3f033933
git-subtree-split: d43c4af0b4

xo-indentlog/example/hello/hello.cpp

@@ -0,0 +1,5 @@
+#include <iostream>
+
+int main(int argc, char ** argv) {
+    std::cout << "Hello, world!" << std::endl;
+}