make: In Doxyfile, fix EXCLUDE for ndnboost to new location include/ndnboost.
diff --git a/Doxyfile b/Doxyfile
index cd86aee..0db8633 100644
--- a/Doxyfile
+++ b/Doxyfile
@@ -700,7 +700,7 @@
 # Note that relative paths are relative to the directory from which doxygen is
 # run.
 
-EXCLUDE                = ndnboost
+EXCLUDE                = include/ndnboost
 
 # The EXCLUDE_SYMLINKS tag can be used to select whether or not files or
 # directories that are symbolic links (a Unix file system feature) are excluded